diff --git a/.travis.yml b/.travis.yml
index 228aba298..ed419dc75 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,9 +1,13 @@
-before_cache: |
-  if command -v cargo; then
-    ! command -v cargo-sweep && cargo install cargo-sweep
-    cargo sweep -i
-    cargo sweep -t 15
-  fi
+before_cache:
+  - |
+    if command -v cargo; then
+      if ! command -v cargo-sweep; then
+        cargo install cargo-sweep
+      fi
+      cargo sweep -i
+      cargo sweep -t 15
+    fi
+  - rm -rf ~/.cargo/registry/src
 
 matrix:
   fast_finish: true
@@ -145,3 +149,44 @@ matrix:
       env:
         - JOBCACHE=7
         - TRAVIS_RUST_VERSION=stable
+
+    - name: Ensure compilation on Redox OS with Redoxer
+      # language: minimal so that it actually uses bionic rather than xenial;
+      # rust isn't yet available on bionic
+      language: minimal
+      dist: bionic
+      if: type = cron
+      cache:
+        cargo: true
+        directories:
+          - $HOME/.redoxer
+          - $HOME/.cargo
+      before_install:
+        # install rust as travis does for language: rust
+        - curl -sSf https://build.travis-ci.org/files/rustup-init.sh | sh -s --
+          --default-toolchain=$TRAVIS_RUST_VERSION -y
+        - export PATH=${TRAVIS_HOME}/.cargo/bin:$PATH
+        - rustc --version
+        - rustup --version
+        - cargo --version
+
+        - sudo apt-get update -qq
+        - sudo apt-get install libfuse-dev
+      install:
+        - if ! command -v redoxer; then cargo install redoxfs redoxer; fi
+        - redoxer install
+      script:
+        - bash redox/uncomment-cargo.sh
+        - redoxer build --verbose
+        - bash redox/comment-cargo.sh
+      before_cache:
+        - |
+          if ! command -v cargo-sweep; then
+            rustup install stable
+            cargo +stable install cargo-sweep
+          fi
+        - cargo sweep -t 15
+        - rm -rf ~/.cargo/registry/src
+      env:
+        - JOBCACHE=10
+        - TRAVIS_RUST_VERSION=nightly
diff --git a/Cargo.lock b/Cargo.lock
index 894e82853..10f220e21 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1,5 +1,10 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+[[package]]
+name = "adler32"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "aho-corasick"
 version = "0.6.10"
@@ -10,7 +15,7 @@ dependencies = [
 
 [[package]]
 name = "aho-corasick"
-version = "0.7.4"
+version = "0.7.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "memchr 2.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -24,22 +29,13 @@ dependencies = [
  "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
-[[package]]
-name = "argon2rs"
-version = "0.2.5"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "blake2-rfc 0.2.18 (registry+https://github.com/rust-lang/crates.io-index)",
- "scoped_threadpool 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
 [[package]]
 name = "arr_macro"
 version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "arr_macro_impl 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "proc-macro-hack 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro-hack 0.5.9 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -47,11 +43,16 @@ name = "arr_macro_impl"
 version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro-hack 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro-hack 0.5.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 0.15.39 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.15.44 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "arrayref"
+version = "0.3.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "arrayvec"
 version = "0.4.11"
@@ -73,7 +74,7 @@ name = "atty"
 version = "0.2.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -84,13 +85,13 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "backtrace"
-version = "0.3.33"
+version = "0.3.34"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "backtrace-sys 0.1.31 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
- "rustc-demangle 0.1.15 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustc-demangle 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -98,8 +99,16 @@ name = "backtrace-sys"
 version = "0.1.31"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cc 1.0.37 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cc 1.0.40 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "base64"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "byteorder 1.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -109,7 +118,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "autocfg 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "byteorder 1.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -138,14 +147,15 @@ dependencies = [
  "byte-tools 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "crypto-mac 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "digest 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "opaque-debug 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "opaque-debug 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
-name = "blake2-rfc"
-version = "0.2.18"
+name = "blake2b_simd"
+version = "0.5.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
+ "arrayref 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "arrayvec 0.4.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "constant_time_eq 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -194,13 +204,13 @@ name = "caseless"
 version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "regex 1.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "unicode-normalization 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "cc"
-version = "1.0.37"
+version = "1.0.40"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -250,7 +260,7 @@ name = "cpython"
 version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "python3-sys 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -263,11 +273,28 @@ dependencies = [
  "build_const 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "crc32fast"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cfg-if 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "crossbeam-utils"
 version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "crossbeam-utils"
+version = "0.6.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cfg-if 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "crypto-mac"
 version = "0.7.0"
@@ -295,8 +322,8 @@ name = "dirs"
 version = "1.0.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
- "redox_users 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_users 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -306,8 +333,8 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "regex 1.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
  "strsim 0.9.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -321,7 +348,7 @@ name = "ena"
 version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -331,8 +358,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "atty 0.2.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "humantime 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "regex 1.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "termcolor 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -341,7 +368,7 @@ name = "failure"
 version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "backtrace 0.3.33 (registry+https://github.com/rust-lang/crates.io-index)",
+ "backtrace 0.3.34 (registry+https://github.com/rust-lang/crates.io-index)",
  "failure_derive 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -352,7 +379,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 0.4.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 0.15.39 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.15.44 (registry+https://github.com/rust-lang/crates.io-index)",
  "synstructure 0.10.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -372,8 +399,8 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "lazy_static 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde_derive 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_derive 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.40 (registry+https://github.com/rust-lang/crates.io-index)",
  "thread-id 3.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -385,7 +412,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "flame 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 0.15.39 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.15.44 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -395,10 +422,21 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "flame 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "indexmap 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.40 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "flate2"
+version = "1.0.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "crc32fast 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libz-sys 1.0.25 (registry+https://github.com/rust-lang/crates.io-index)",
+ "miniz_oxide 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "fnv"
 version = "1.0.6"
@@ -427,7 +465,7 @@ name = "gethostname"
 version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -477,10 +515,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "js-sys"
-version = "0.3.25"
+version = "0.3.26"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "wasm-bindgen 0.2.48 (registry+https://github.com/rust-lang/crates.io-index)",
+ "wasm-bindgen 0.2.49 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -511,10 +549,10 @@ dependencies = [
  "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lalrpop-util 0.16.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "petgraph 0.4.13 (registry+https://github.com/rust-lang/crates.io-index)",
- "regex 1.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
- "regex-syntax 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde_derive 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex-syntax 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_derive 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
  "sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "string_cache 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "term 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -538,42 +576,53 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "lexical"
-version = "2.2.1"
+version = "2.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
- "lexical-core 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lexical-core 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "lexical-core"
-version = "0.4.2"
+version = "0.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "ryu 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ryu 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "stackvector 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "static_assertions 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "static_assertions 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "libc"
-version = "0.2.60"
+version = "0.2.62"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "libz-sys"
+version = "1.0.25"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cc 1.0.40 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pkg-config 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
+ "vcpkg 0.2.7 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "log"
 version = "0.3.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "log"
-version = "0.4.7"
+version = "0.4.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -596,7 +645,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "block-buffer 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "digest 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "opaque-debug 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "opaque-debug 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -604,6 +653,14 @@ name = "memchr"
 version = "2.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "miniz_oxide"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "adler32 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "new_debug_unreachable"
 version = "1.0.3"
@@ -615,9 +672,9 @@ version = "0.13.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "bitflags 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "cc 1.0.37 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cc 1.0.40 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
  "void 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -627,9 +684,9 @@ version = "0.14.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "bitflags 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "cc 1.0.37 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cc 1.0.40 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
  "void 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -654,7 +711,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "num-integer 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -663,7 +720,7 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "num-traits 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -674,6 +731,16 @@ dependencies = [
  "num-traits 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "num-iter"
+version = "0.1.39"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "autocfg 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-integer 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "num-rational"
 version = "0.2.1"
@@ -689,9 +756,17 @@ name = "num-traits"
 version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "num_cpus"
+version = "1.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "opaque-debug"
-version = "0.2.2"
+version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -725,6 +800,11 @@ dependencies = [
  "siphasher 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "pkg-config"
+version = "0.3.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "precomputed-hash"
 version = "0.1.1"
@@ -732,12 +812,12 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "proc-macro-hack"
-version = "0.5.8"
+version = "0.5.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 0.4.30 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 0.15.39 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -748,13 +828,21 @@ dependencies = [
  "unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "proc-macro2"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "pwd"
 version = "1.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "failure 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -762,8 +850,8 @@ name = "python3-sys"
 version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
- "regex 1.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -779,6 +867,14 @@ dependencies = [
  "proc-macro2 0.4.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "quote"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "rand"
 version = "0.5.6"
@@ -786,7 +882,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "fuchsia-cprng 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -797,9 +893,9 @@ version = "0.6.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "autocfg 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_chacha 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_hc 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_isaac 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_jitter 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -823,12 +919,12 @@ name = "rand_core"
 version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "rand_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "rand_core"
-version = "0.4.0"
+version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -852,8 +948,8 @@ name = "rand_jitter"
 version = "0.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -864,8 +960,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "fuchsia-cprng 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "rdrand 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -876,7 +972,7 @@ version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "autocfg 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -902,13 +998,13 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "redox_users"
-version = "0.3.0"
+version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "argon2rs 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "failure 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_os 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rust-argon2 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -920,19 +1016,18 @@ dependencies = [
  "memchr 2.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex-syntax 0.5.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "thread_local 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "utf8-ranges 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "utf8-ranges 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "regex"
-version = "1.1.9"
+version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "aho-corasick 0.7.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "aho-corasick 0.7.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "memchr 2.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "regex-syntax 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex-syntax 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "thread_local 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "utf8-ranges 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -940,20 +1035,27 @@ name = "regex-syntax"
 version = "0.5.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "ucd-util 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ucd-util 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "regex-syntax"
-version = "0.6.8"
+version = "0.6.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "rust-argon2"
+version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "ucd-util 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "base64 0.10.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "blake2b_simd 0.5.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "crossbeam-utils 0.6.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "rustc-demangle"
-version = "0.1.15"
+version = "0.1.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -982,7 +1084,7 @@ dependencies = [
  "env_logger 0.5.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "flame 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "flamescope 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustpython-compiler 0.1.0",
  "rustpython-parser 0.1.0",
  "rustpython-vm 0.1.0",
@@ -997,7 +1099,7 @@ dependencies = [
  "bitflags 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-bigint 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-complex 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1018,12 +1120,12 @@ version = "0.1.0"
 dependencies = [
  "bincode 1.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "maplit 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "proc-macro-hack 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro-hack 0.5.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "proc-macro2 0.4.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustpython-bytecode 0.1.0",
  "rustpython-compiler 0.1.0",
- "syn 0.15.39 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.15.44 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1032,7 +1134,7 @@ version = "0.1.0"
 dependencies = [
  "lalrpop 0.16.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "lalrpop-util 0.16.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-bigint 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1045,6 +1147,7 @@ dependencies = [
 name = "rustpython-vm"
 version = "0.1.0"
 dependencies = [
+ "adler32 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "arr_macro 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "bincode 1.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "bitflags 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1053,17 +1156,21 @@ dependencies = [
  "caseless 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "chrono 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "crc 1.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "crc32fast 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "digest 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "flame 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "flamer 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "flate2 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "gethostname 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "hex 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "hexf-parse 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "indexmap 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "lexical 2.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lexical 2.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libz-sys 1.0.25 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "maplit 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "md-5 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1071,18 +1178,20 @@ dependencies = [
  "num-bigint 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-complex 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-integer 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-iter 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-rational 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "proc-macro-hack 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num_cpus 1.10.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro-hack 0.5.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "pwd 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.5.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "regex 1.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc_version_runtime 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustpython-bytecode 0.1.0",
  "rustpython-compiler 0.1.0",
  "rustpython-derive 0.1.0",
  "rustpython-parser 0.1.0",
- "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.40 (registry+https://github.com/rust-lang/crates.io-index)",
  "sha-1 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1104,16 +1213,16 @@ version = "0.1.0-pre-alpha.2"
 dependencies = [
  "cfg-if 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures 0.1.28 (registry+https://github.com/rust-lang/crates.io-index)",
- "js-sys 0.3.25 (registry+https://github.com/rust-lang/crates.io-index)",
+ "js-sys 0.3.26 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustpython-compiler 0.1.0",
  "rustpython-parser 0.1.0",
  "rustpython-vm 0.1.0",
- "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde-wasm-bindgen 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "wasm-bindgen 0.2.48 (registry+https://github.com/rust-lang/crates.io-index)",
- "wasm-bindgen-futures 0.3.25 (registry+https://github.com/rust-lang/crates.io-index)",
- "web-sys 0.3.25 (registry+https://github.com/rust-lang/crates.io-index)",
+ "wasm-bindgen 0.2.49 (registry+https://github.com/rust-lang/crates.io-index)",
+ "wasm-bindgen-futures 0.3.26 (registry+https://github.com/rust-lang/crates.io-index)",
+ "web-sys 0.3.26 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1122,8 +1231,8 @@ version = "4.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "dirs 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
- "log 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "memchr 2.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "nix 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "unicode-segmentation 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1132,21 +1241,11 @@ dependencies = [
  "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
-[[package]]
-name = "ryu"
-version = "0.2.8"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-
 [[package]]
 name = "ryu"
 version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
-[[package]]
-name = "scoped_threadpool"
-version = "0.1.9"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-
 [[package]]
 name = "semver"
 version = "0.9.0"
@@ -1162,10 +1261,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "serde"
-version = "1.0.97"
+version = "1.0.98"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "serde_derive 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_derive 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1174,19 +1273,19 @@ version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "fnv 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "js-sys 0.3.25 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
- "wasm-bindgen 0.2.48 (registry+https://github.com/rust-lang/crates.io-index)",
+ "js-sys 0.3.26 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
+ "wasm-bindgen 0.2.49 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.97"
+version = "1.0.98"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 0.4.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 0.15.39 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.15.44 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1196,7 +1295,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "itoa 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "ryu 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1207,7 +1306,7 @@ dependencies = [
  "block-buffer 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "digest 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "fake-simd 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "opaque-debug 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "opaque-debug 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1218,7 +1317,7 @@ dependencies = [
  "block-buffer 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "digest 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "fake-simd 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "opaque-debug 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "opaque-debug 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1230,7 +1329,7 @@ dependencies = [
  "byte-tools 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "digest 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "keccak 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "opaque-debug 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "opaque-debug 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1259,7 +1358,7 @@ dependencies = [
 
 [[package]]
 name = "static_assertions"
-version = "0.2.5"
+version = "0.3.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -1279,7 +1378,7 @@ dependencies = [
  "new_debug_unreachable 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "phf_shared 0.7.24 (registry+https://github.com/rust-lang/crates.io-index)",
  "precomputed-hash 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.98 (registry+https://github.com/rust-lang/crates.io-index)",
  "string_cache_codegen 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "string_cache_shared 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1317,7 +1416,7 @@ version = "0.1.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "crossbeam-utils 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1328,7 +1427,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "syn"
-version = "0.15.39"
+version = "0.15.44"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 0.4.30 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1336,6 +1435,16 @@ dependencies = [
  "unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "syn"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "synstructure"
 version = "0.10.2"
@@ -1343,7 +1452,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 0.4.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 0.15.39 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.15.44 (registry+https://github.com/rust-lang/crates.io-index)",
  "unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1377,7 +1486,7 @@ name = "thread-id"
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 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1395,7 +1504,7 @@ name = "time"
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 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
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@@ -1407,7 +1516,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "ucd-util"
-version = "0.1.3"
+version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -1706,6 +1815,11 @@ name = "unicode-xid"
 version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "unicode-xid"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "unicode_categories"
 version = "0.1.1"
@@ -1726,7 +1840,7 @@ dependencies = [
 
 [[package]]
 name = "utf8-ranges"
-version = "1.0.3"
+version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -1734,6 +1848,11 @@ name = "utf8parse"
 version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "vcpkg"
+version = "0.2.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
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@@ -1751,87 +1870,90 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
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-version = "0.2.48"
+version = "0.2.49"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "wasm-bindgen-macro 0.2.48 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "wasm-bindgen-macro 0.2.49 (registry+https://github.com/rust-lang/crates.io-index)",
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 [[package]]
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 [[package]]
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diff --git a/Cargo.toml b/Cargo.toml
index b55f47497..56d5a2138 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -42,8 +42,9 @@ version = "0.2"
 name = "rustpython"
 path = "src/main.rs"
 
-# Uncommment when you want to compile/check with redoxer
-# [patch.crates-io]
+[patch.crates-io]
+# REDOX START, Uncommment when you want to compile/check with redoxer
 # time = { git = "https://gitlab.redox-os.org/redox-os/time.git", branch = "redox-unix" }
 # libc = { git = "https://github.com/AdminXVII/libc",	branch = "extra-traits-redox" }
 # nix = { git = "https://github.com/AdminXVII/nix",	branch = "add-redox-support" }
+# REDOX END
diff --git a/DEVELOPMENT.md b/DEVELOPMENT.md
index 9fd818536..7ddf53fc6 100644
--- a/DEVELOPMENT.md
+++ b/DEVELOPMENT.md
@@ -1,9 +1,91 @@
 # RustPython Development Guide and Tips
 
+RustPython attracts developers with interest and experience in Rust, Python,
+or WebAssembly. Whether you are familiar with Rust, Python, or 
+WebAssembly, the goal of this Development Guide is to give you the basics to
+get set up for developing RustPython and contributing to this project. 
+
+The contents of the Development Guide include:
+
+- [Setting up a development environment](#setting-up-a-development-environment)
+- [Code style](#code-style)
+- [Testing](#testing)
+- [Profiling](#profiling)
+- [Code organization](#code-organization)
+- [Understanding internals](#understanding-internals)
+- [Questions](#questions)
+
+## Setting up a development environment
+
+RustPython requires the following:
+
+- Rust 1.36 or higher
+    - To check Rust version: `rustc --version` 
+    - If you have `rustup` on your system, enter to update to the latest
+      stable version: `rustup update stable`
+    - If you do not have Rust installed, use [rustup](https://rustup.rs/) to
+      do so.
+- CPython version 3.7.4 or higher
+    - CPython can be installed by your operating system's package manager,
+      from the [Python website](https://www.python.org/downloads/), or
+      using a third-party distribution, such as 
+      [Anaconda](https://www.anaconda.com/distribution/).
+- [Optional] The Python package, `pytest`, is used for testing Python code
+  snippets. To install, enter `python3 -m pip install pytest`.
+
+## Code style
+
+The Rust code style used is the default
+[rustfmt](https://github.com/rust-lang/rustfmt) codestyle. Please format your
+code accordingly. We also use [clippy](https://github.com/rust-lang/rust-clippy)
+to detect rust code issues. 
+
+Python code should follow the 
+[PEP 8](https://www.python.org/dev/peps/pep-0008/) style. We also use
+[flake8](http://flake8.pycqa.org/en/latest/) to check Python code style.
+
+## Testing
+
+To test RustPython's functionality, a collection of Python snippets is located
+in the `tests/snippets` directory and can be run using `pytest`:
+
+```shell
+$ cd tests
+$ pytest -v
+```
+
+Rust unit tests can be run with `cargo`:
+
+```shell
+$ cargo test --all
+```
+
+## Profiling
+
+To profile RustPython, build it in `release` mode with the `flame-it` feature.
+This will generate a file `flamescope.json`, which can be viewed at
+https://speedscope.app.
+
+```shell
+$ cargo run --release --features flame-it script.py
+$ cat flamescope.json
+{<json>}
+```
+
+You can specify another file name other than the default by using the
+`--output-file` option to specify a file name (or `stdout` if you specify `-`).
+The `--output-format` option determines the format of the output file.
+The speedscope json format (default), text, or raw html can be passed. There
+exists a raw html viewer which is currently broken, and we welcome a PR to fix it.
+
 ## Code organization
 
+Understanding a new codebase takes time. Here's a brief view of the
+repository's structure:
+
 - `bytecode/src`: python bytecode representation in rust structures
 - `compiler/src`: python compilation to bytecode
+- `derive/src`: Rust language extensions and macros specific to rustpython
 - `parser/src`: python lexing, parsing and ast
 - `Lib`: Carefully selected / copied files from CPython sourcecode. This is
    the python side of the standard library.
@@ -19,42 +101,67 @@
 - `wasm`: Binary crate and resources for WebAssembly build
 - `tests`: integration test snippets
 
-## Code style
+## Understanding Internals
 
-The code style used is the default
-[rustfmt](https://github.com/rust-lang/rustfmt) codestyle. Please format your
-code accordingly. We also use [clippy](https://github.com/rust-lang/rust-clippy)
-to detect rust code issues.
+The RustPython workspace includes the `rustpython` top-level crate. The `Cargo.toml`
+file in the root of the repo provide configuration of the crate and the
+implementation is found in the `src` directory (specifically, 
+`src/main.rs`).
 
-## Testing
+The top-level `rustpython` binary depends on several lower-level crates including:
 
-To test rustpython, there is a collection of python snippets located in the
-`tests/snippets` directory. To run those tests do the following:
+- `rustpython-parser` (implementation in `parser/src`)
+- `rustpython-compiler` (implementation in `compiler/src`)
+- `rustpython-vm` (implementation in `vm/src`)
 
-```shell
-$ cd tests
-$ pytest -v
-```
+Together, these crates provide the functions of a programming language and
+enable a line of code to go through a series of steps:
 
-There also are some unit tests, you can run those with cargo:
+- parse the line of source code into tokens
+- determine if the tokens are valid syntax
+- create an Abstract Syntax Tree (AST)
+- compile the AST into bytecode
+- execute the bytecode in the virtual machine (VM).
 
-```shell
-$ cargo test --all
-```
+### rustpython-parser
 
-## Profiling
+This crate contains the lexer and parser to convert a line of code to
+an Abstract Syntax Tree (AST):
 
-To profile rustpython, simply build in release mode with the `flame-it` feature.
-This will generate a file `flamescope.json`, which you can then view at
-https://speedscope.app.
+- Lexer: `parser/lexer.rs` converts Python source code into tokens
+- Parser: `parser/parser.rs` takes the tokens generated by the lexer and parses
+  the tokens into an AST (Abstract Syntax Tree) where the nodes of the syntax
+  tree are Rust structs and enums.
+  - The Parser relies on `LALRPOP`, a Rust parser generator framework.
+  - More information on parsers and a tutorial can be found in the 
+    [LALRPOP book](https://lalrpop.github.io/lalrpop/README.html).
+- AST: `parser/ast.rs` implements in Rust the Python types and expressions
+  represented by the AST nodes.
 
-```sh
-$ cargo run --release --features flame-it script.py
-$ cat flamescope.json
-{<json>}
-```
+### rustpython-compiler
 
-You can also pass the `--output-file` option to choose which file to output to
-(or stdout if you specify `-`), and the `--output-format` option to choose if
-you want to output in the speedscope json format (default), text, or a raw html
-viewer (currently broken).
+The `rustpython-compiler` crate's purpose is to transform the AST (Abstract Syntax
+Tree) to bytecode. The implementation of the compiler is found in the
+`compiler/src` directory. The compiler implements Python's peephole optimizer
+implementation, Symbol table, and streams in Rust.
+
+Implementation of bytecode structure in Rust is found in the `bytecode/src`
+directory. The `bytecode/src/bytecode.rs` contains the representation of
+instructions and operations in Rust. Further information about Python's
+bytecode instructions can be found in the
+[Python documentation](https://docs.python.org/3/library/dis.html#bytecodes).
+
+### rustpython-vm
+
+The `rustpython-vm` crate has the important job of running the virtual machine that
+executes Python's instructions. The `vm/src` directory contains code to
+implement the read and evaluation loop that fetches and dispatches
+instructions. This directory also contains the implementation of the
+Python Standard Library modules in Rust (`vm/src/stdlib`). In Python
+everything can be represented as an Object. `vm/src/obj` directory holds
+the Rust code used to represent a Python Object and its methods.
+
+## Questions
+
+Have you tried these steps and have a question, please chat with us on
+[gitter](https://gitter.im/rustpython/Lobby).
diff --git a/Lib/aifc.py b/Lib/aifc.py
new file mode 100644
index 000000000..1916e7ef8
--- /dev/null
+++ b/Lib/aifc.py
@@ -0,0 +1,951 @@
+"""Stuff to parse AIFF-C and AIFF files.
+
+Unless explicitly stated otherwise, the description below is true
+both for AIFF-C files and AIFF files.
+
+An AIFF-C file has the following structure.
+
+  +-----------------+
+  | FORM            |
+  +-----------------+
+  | <size>          |
+  +----+------------+
+  |    | AIFC       |
+  |    +------------+
+  |    | <chunks>   |
+  |    |    .       |
+  |    |    .       |
+  |    |    .       |
+  +----+------------+
+
+An AIFF file has the string "AIFF" instead of "AIFC".
+
+A chunk consists of an identifier (4 bytes) followed by a size (4 bytes,
+big endian order), followed by the data.  The size field does not include
+the size of the 8 byte header.
+
+The following chunk types are recognized.
+
+  FVER
+      <version number of AIFF-C defining document> (AIFF-C only).
+  MARK
+      <# of markers> (2 bytes)
+      list of markers:
+          <marker ID> (2 bytes, must be > 0)
+          <position> (4 bytes)
+          <marker name> ("pstring")
+  COMM
+      <# of channels> (2 bytes)
+      <# of sound frames> (4 bytes)
+      <size of the samples> (2 bytes)
+      <sampling frequency> (10 bytes, IEEE 80-bit extended
+          floating point)
+      in AIFF-C files only:
+      <compression type> (4 bytes)
+      <human-readable version of compression type> ("pstring")
+  SSND
+      <offset> (4 bytes, not used by this program)
+      <blocksize> (4 bytes, not used by this program)
+      <sound data>
+
+A pstring consists of 1 byte length, a string of characters, and 0 or 1
+byte pad to make the total length even.
+
+Usage.
+
+Reading AIFF files:
+  f = aifc.open(file, 'r')
+where file is either the name of a file or an open file pointer.
+The open file pointer must have methods read(), seek(), and close().
+In some types of audio files, if the setpos() method is not used,
+the seek() method is not necessary.
+
+This returns an instance of a class with the following public methods:
+  getnchannels()  -- returns number of audio channels (1 for
+             mono, 2 for stereo)
+  getsampwidth()  -- returns sample width in bytes
+  getframerate()  -- returns sampling frequency
+  getnframes()    -- returns number of audio frames
+  getcomptype()   -- returns compression type ('NONE' for AIFF files)
+  getcompname()   -- returns human-readable version of
+             compression type ('not compressed' for AIFF files)
+  getparams() -- returns a namedtuple consisting of all of the
+             above in the above order
+  getmarkers()    -- get the list of marks in the audio file or None
+             if there are no marks
+  getmark(id) -- get mark with the specified id (raises an error
+             if the mark does not exist)
+  readframes(n)   -- returns at most n frames of audio
+  rewind()    -- rewind to the beginning of the audio stream
+  setpos(pos) -- seek to the specified position
+  tell()      -- return the current position
+  close()     -- close the instance (make it unusable)
+The position returned by tell(), the position given to setpos() and
+the position of marks are all compatible and have nothing to do with
+the actual position in the file.
+The close() method is called automatically when the class instance
+is destroyed.
+
+Writing AIFF files:
+  f = aifc.open(file, 'w')
+where file is either the name of a file or an open file pointer.
+The open file pointer must have methods write(), tell(), seek(), and
+close().
+
+This returns an instance of a class with the following public methods:
+  aiff()      -- create an AIFF file (AIFF-C default)
+  aifc()      -- create an AIFF-C file
+  setnchannels(n) -- set the number of channels
+  setsampwidth(n) -- set the sample width
+  setframerate(n) -- set the frame rate
+  setnframes(n)   -- set the number of frames
+  setcomptype(type, name)
+          -- set the compression type and the
+             human-readable compression type
+  setparams(tuple)
+          -- set all parameters at once
+  setmark(id, pos, name)
+          -- add specified mark to the list of marks
+  tell()      -- return current position in output file (useful
+             in combination with setmark())
+  writeframesraw(data)
+          -- write audio frames without pathing up the
+             file header
+  writeframes(data)
+          -- write audio frames and patch up the file header
+  close()     -- patch up the file header and close the
+             output file
+You should set the parameters before the first writeframesraw or
+writeframes.  The total number of frames does not need to be set,
+but when it is set to the correct value, the header does not have to
+be patched up.
+It is best to first set all parameters, perhaps possibly the
+compression type, and then write audio frames using writeframesraw.
+When all frames have been written, either call writeframes(b'') or
+close() to patch up the sizes in the header.
+Marks can be added anytime.  If there are any marks, you must call
+close() after all frames have been written.
+The close() method is called automatically when the class instance
+is destroyed.
+
+When a file is opened with the extension '.aiff', an AIFF file is
+written, otherwise an AIFF-C file is written.  This default can be
+changed by calling aiff() or aifc() before the first writeframes or
+writeframesraw.
+"""
+
+import struct
+import builtins
+import warnings
+
+__all__ = ["Error", "open", "openfp"]
+
+class Error(Exception):
+    pass
+
+_AIFC_version = 0xA2805140     # Version 1 of AIFF-C
+
+def _read_long(file):
+    try:
+        return struct.unpack('>l', file.read(4))[0]
+    except struct.error:
+        raise EOFError from None
+
+def _read_ulong(file):
+    try:
+        return struct.unpack('>L', file.read(4))[0]
+    except struct.error:
+        raise EOFError from None
+
+def _read_short(file):
+    try:
+        return struct.unpack('>h', file.read(2))[0]
+    except struct.error:
+        raise EOFError from None
+
+def _read_ushort(file):
+    try:
+        return struct.unpack('>H', file.read(2))[0]
+    except struct.error:
+        raise EOFError from None
+
+def _read_string(file):
+    length = ord(file.read(1))
+    if length == 0:
+        data = b''
+    else:
+        data = file.read(length)
+    if length & 1 == 0:
+        dummy = file.read(1)
+    return data
+
+_HUGE_VAL = 1.79769313486231e+308 # See <limits.h>
+
+def _read_float(f): # 10 bytes
+    expon = _read_short(f) # 2 bytes
+    sign = 1
+    if expon < 0:
+        sign = -1
+        expon = expon + 0x8000
+    himant = _read_ulong(f) # 4 bytes
+    lomant = _read_ulong(f) # 4 bytes
+    if expon == himant == lomant == 0:
+        f = 0.0
+    elif expon == 0x7FFF:
+        f = _HUGE_VAL
+    else:
+        expon = expon - 16383
+        f = (himant * 0x100000000 + lomant) * pow(2.0, expon - 63)
+    return sign * f
+
+def _write_short(f, x):
+    f.write(struct.pack('>h', x))
+
+def _write_ushort(f, x):
+    f.write(struct.pack('>H', x))
+
+def _write_long(f, x):
+    f.write(struct.pack('>l', x))
+
+def _write_ulong(f, x):
+    f.write(struct.pack('>L', x))
+
+def _write_string(f, s):
+    if len(s) > 255:
+        raise ValueError("string exceeds maximum pstring length")
+    f.write(struct.pack('B', len(s)))
+    f.write(s)
+    if len(s) & 1 == 0:
+        f.write(b'\x00')
+
+def _write_float(f, x):
+    import math
+    if x < 0:
+        sign = 0x8000
+        x = x * -1
+    else:
+        sign = 0
+    if x == 0:
+        expon = 0
+        himant = 0
+        lomant = 0
+    else:
+        fmant, expon = math.frexp(x)
+        if expon > 16384 or fmant >= 1 or fmant != fmant: # Infinity or NaN
+            expon = sign|0x7FFF
+            himant = 0
+            lomant = 0
+        else:                   # Finite
+            expon = expon + 16382
+            if expon < 0:           # denormalized
+                fmant = math.ldexp(fmant, expon)
+                expon = 0
+            expon = expon | sign
+            fmant = math.ldexp(fmant, 32)
+            fsmant = math.floor(fmant)
+            himant = int(fsmant)
+            fmant = math.ldexp(fmant - fsmant, 32)
+            fsmant = math.floor(fmant)
+            lomant = int(fsmant)
+    _write_ushort(f, expon)
+    _write_ulong(f, himant)
+    _write_ulong(f, lomant)
+
+from chunk import Chunk
+from collections import namedtuple
+
+_aifc_params = namedtuple('_aifc_params',
+                          'nchannels sampwidth framerate nframes comptype compname')
+
+_aifc_params.nchannels.__doc__ = 'Number of audio channels (1 for mono, 2 for stereo)'
+_aifc_params.sampwidth.__doc__ = 'Sample width in bytes'
+_aifc_params.framerate.__doc__ = 'Sampling frequency'
+_aifc_params.nframes.__doc__ = 'Number of audio frames'
+_aifc_params.comptype.__doc__ = 'Compression type ("NONE" for AIFF files)'
+_aifc_params.compname.__doc__ = ("""\
+A human-readable version of the compression type
+('not compressed' for AIFF files)""")
+
+
+class Aifc_read:
+    # Variables used in this class:
+    #
+    # These variables are available to the user though appropriate
+    # methods of this class:
+    # _file -- the open file with methods read(), close(), and seek()
+    #       set through the __init__() method
+    # _nchannels -- the number of audio channels
+    #       available through the getnchannels() method
+    # _nframes -- the number of audio frames
+    #       available through the getnframes() method
+    # _sampwidth -- the number of bytes per audio sample
+    #       available through the getsampwidth() method
+    # _framerate -- the sampling frequency
+    #       available through the getframerate() method
+    # _comptype -- the AIFF-C compression type ('NONE' if AIFF)
+    #       available through the getcomptype() method
+    # _compname -- the human-readable AIFF-C compression type
+    #       available through the getcomptype() method
+    # _markers -- the marks in the audio file
+    #       available through the getmarkers() and getmark()
+    #       methods
+    # _soundpos -- the position in the audio stream
+    #       available through the tell() method, set through the
+    #       setpos() method
+    #
+    # These variables are used internally only:
+    # _version -- the AIFF-C version number
+    # _decomp -- the decompressor from builtin module cl
+    # _comm_chunk_read -- 1 iff the COMM chunk has been read
+    # _aifc -- 1 iff reading an AIFF-C file
+    # _ssnd_seek_needed -- 1 iff positioned correctly in audio
+    #       file for readframes()
+    # _ssnd_chunk -- instantiation of a chunk class for the SSND chunk
+    # _framesize -- size of one frame in the file
+
+    _file = None  # Set here since __del__ checks it
+
+    def initfp(self, file):
+        self._version = 0
+        self._convert = None
+        self._markers = []
+        self._soundpos = 0
+        self._file = file
+        chunk = Chunk(file)
+        if chunk.getname() != b'FORM':
+            raise Error('file does not start with FORM id')
+        formdata = chunk.read(4)
+        if formdata == b'AIFF':
+            self._aifc = 0
+        elif formdata == b'AIFC':
+            self._aifc = 1
+        else:
+            raise Error('not an AIFF or AIFF-C file')
+        self._comm_chunk_read = 0
+        self._ssnd_chunk = None
+        while 1:
+            self._ssnd_seek_needed = 1
+            try:
+                chunk = Chunk(self._file)
+            except EOFError:
+                break
+            chunkname = chunk.getname()
+            if chunkname == b'COMM':
+                self._read_comm_chunk(chunk)
+                self._comm_chunk_read = 1
+            elif chunkname == b'SSND':
+                self._ssnd_chunk = chunk
+                dummy = chunk.read(8)
+                self._ssnd_seek_needed = 0
+            elif chunkname == b'FVER':
+                self._version = _read_ulong(chunk)
+            elif chunkname == b'MARK':
+                self._readmark(chunk)
+            chunk.skip()
+        if not self._comm_chunk_read or not self._ssnd_chunk:
+            raise Error('COMM chunk and/or SSND chunk missing')
+
+    def __init__(self, f):
+        if isinstance(f, str):
+            file_object = builtins.open(f, 'rb')
+            try:
+                self.initfp(file_object)
+            except:
+                file_object.close()
+                raise
+        else:
+            # assume it is an open file object already
+            self.initfp(f)
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        self.close()
+
+    #
+    # User visible methods.
+    #
+    def getfp(self):
+        return self._file
+
+    def rewind(self):
+        self._ssnd_seek_needed = 1
+        self._soundpos = 0
+
+    def close(self):
+        file = self._file
+        if file is not None:
+            self._file = None
+            file.close()
+
+    def tell(self):
+        return self._soundpos
+
+    def getnchannels(self):
+        return self._nchannels
+
+    def getnframes(self):
+        return self._nframes
+
+    def getsampwidth(self):
+        return self._sampwidth
+
+    def getframerate(self):
+        return self._framerate
+
+    def getcomptype(self):
+        return self._comptype
+
+    def getcompname(self):
+        return self._compname
+
+##  def getversion(self):
+##      return self._version
+
+    def getparams(self):
+        return _aifc_params(self.getnchannels(), self.getsampwidth(),
+                            self.getframerate(), self.getnframes(),
+                            self.getcomptype(), self.getcompname())
+
+    def getmarkers(self):
+        if len(self._markers) == 0:
+            return None
+        return self._markers
+
+    def getmark(self, id):
+        for marker in self._markers:
+            if id == marker[0]:
+                return marker
+        raise Error('marker {0!r} does not exist'.format(id))
+
+    def setpos(self, pos):
+        if pos < 0 or pos > self._nframes:
+            raise Error('position not in range')
+        self._soundpos = pos
+        self._ssnd_seek_needed = 1
+
+    def readframes(self, nframes):
+        if self._ssnd_seek_needed:
+            self._ssnd_chunk.seek(0)
+            dummy = self._ssnd_chunk.read(8)
+            pos = self._soundpos * self._framesize
+            if pos:
+                self._ssnd_chunk.seek(pos + 8)
+            self._ssnd_seek_needed = 0
+        if nframes == 0:
+            return b''
+        data = self._ssnd_chunk.read(nframes * self._framesize)
+        if self._convert and data:
+            data = self._convert(data)
+        self._soundpos = self._soundpos + len(data) // (self._nchannels
+                                                        * self._sampwidth)
+        return data
+
+    #
+    # Internal methods.
+    #
+
+    def _alaw2lin(self, data):
+        import audioop
+        return audioop.alaw2lin(data, 2)
+
+    def _ulaw2lin(self, data):
+        import audioop
+        return audioop.ulaw2lin(data, 2)
+
+    def _adpcm2lin(self, data):
+        import audioop
+        if not hasattr(self, '_adpcmstate'):
+            # first time
+            self._adpcmstate = None
+        data, self._adpcmstate = audioop.adpcm2lin(data, 2, self._adpcmstate)
+        return data
+
+    def _read_comm_chunk(self, chunk):
+        self._nchannels = _read_short(chunk)
+        self._nframes = _read_long(chunk)
+        self._sampwidth = (_read_short(chunk) + 7) // 8
+        self._framerate = int(_read_float(chunk))
+        if self._sampwidth <= 0:
+            raise Error('bad sample width')
+        if self._nchannels <= 0:
+            raise Error('bad # of channels')
+        self._framesize = self._nchannels * self._sampwidth
+        if self._aifc:
+            #DEBUG: SGI's soundeditor produces a bad size :-(
+            kludge = 0
+            if chunk.chunksize == 18:
+                kludge = 1
+                warnings.warn('Warning: bad COMM chunk size')
+                chunk.chunksize = 23
+            #DEBUG end
+            self._comptype = chunk.read(4)
+            #DEBUG start
+            if kludge:
+                length = ord(chunk.file.read(1))
+                if length & 1 == 0:
+                    length = length + 1
+                chunk.chunksize = chunk.chunksize + length
+                chunk.file.seek(-1, 1)
+            #DEBUG end
+            self._compname = _read_string(chunk)
+            if self._comptype != b'NONE':
+                if self._comptype == b'G722':
+                    self._convert = self._adpcm2lin
+                elif self._comptype in (b'ulaw', b'ULAW'):
+                    self._convert = self._ulaw2lin
+                elif self._comptype in (b'alaw', b'ALAW'):
+                    self._convert = self._alaw2lin
+                else:
+                    raise Error('unsupported compression type')
+                self._sampwidth = 2
+        else:
+            self._comptype = b'NONE'
+            self._compname = b'not compressed'
+
+    def _readmark(self, chunk):
+        nmarkers = _read_short(chunk)
+        # Some files appear to contain invalid counts.
+        # Cope with this by testing for EOF.
+        try:
+            for i in range(nmarkers):
+                id = _read_short(chunk)
+                pos = _read_long(chunk)
+                name = _read_string(chunk)
+                if pos or name:
+                    # some files appear to have
+                    # dummy markers consisting of
+                    # a position 0 and name ''
+                    self._markers.append((id, pos, name))
+        except EOFError:
+            w = ('Warning: MARK chunk contains only %s marker%s instead of %s' %
+                 (len(self._markers), '' if len(self._markers) == 1 else 's',
+                  nmarkers))
+            warnings.warn(w)
+
+class Aifc_write:
+    # Variables used in this class:
+    #
+    # These variables are user settable through appropriate methods
+    # of this class:
+    # _file -- the open file with methods write(), close(), tell(), seek()
+    #       set through the __init__() method
+    # _comptype -- the AIFF-C compression type ('NONE' in AIFF)
+    #       set through the setcomptype() or setparams() method
+    # _compname -- the human-readable AIFF-C compression type
+    #       set through the setcomptype() or setparams() method
+    # _nchannels -- the number of audio channels
+    #       set through the setnchannels() or setparams() method
+    # _sampwidth -- the number of bytes per audio sample
+    #       set through the setsampwidth() or setparams() method
+    # _framerate -- the sampling frequency
+    #       set through the setframerate() or setparams() method
+    # _nframes -- the number of audio frames written to the header
+    #       set through the setnframes() or setparams() method
+    # _aifc -- whether we're writing an AIFF-C file or an AIFF file
+    #       set through the aifc() method, reset through the
+    #       aiff() method
+    #
+    # These variables are used internally only:
+    # _version -- the AIFF-C version number
+    # _comp -- the compressor from builtin module cl
+    # _nframeswritten -- the number of audio frames actually written
+    # _datalength -- the size of the audio samples written to the header
+    # _datawritten -- the size of the audio samples actually written
+
+    _file = None  # Set here since __del__ checks it
+
+    def __init__(self, f):
+        if isinstance(f, str):
+            file_object = builtins.open(f, 'wb')
+            try:
+                self.initfp(file_object)
+            except:
+                file_object.close()
+                raise
+
+            # treat .aiff file extensions as non-compressed audio
+            if f.endswith('.aiff'):
+                self._aifc = 0
+        else:
+            # assume it is an open file object already
+            self.initfp(f)
+
+    def initfp(self, file):
+        self._file = file
+        self._version = _AIFC_version
+        self._comptype = b'NONE'
+        self._compname = b'not compressed'
+        self._convert = None
+        self._nchannels = 0
+        self._sampwidth = 0
+        self._framerate = 0
+        self._nframes = 0
+        self._nframeswritten = 0
+        self._datawritten = 0
+        self._datalength = 0
+        self._markers = []
+        self._marklength = 0
+        self._aifc = 1      # AIFF-C is default
+
+    def __del__(self):
+        self.close()
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        self.close()
+
+    #
+    # User visible methods.
+    #
+    def aiff(self):
+        if self._nframeswritten:
+            raise Error('cannot change parameters after starting to write')
+        self._aifc = 0
+
+    def aifc(self):
+        if self._nframeswritten:
+            raise Error('cannot change parameters after starting to write')
+        self._aifc = 1
+
+    def setnchannels(self, nchannels):
+        if self._nframeswritten:
+            raise Error('cannot change parameters after starting to write')
+        if nchannels < 1:
+            raise Error('bad # of channels')
+        self._nchannels = nchannels
+
+    def getnchannels(self):
+        if not self._nchannels:
+            raise Error('number of channels not set')
+        return self._nchannels
+
+    def setsampwidth(self, sampwidth):
+        if self._nframeswritten:
+            raise Error('cannot change parameters after starting to write')
+        if sampwidth < 1 or sampwidth > 4:
+            raise Error('bad sample width')
+        self._sampwidth = sampwidth
+
+    def getsampwidth(self):
+        if not self._sampwidth:
+            raise Error('sample width not set')
+        return self._sampwidth
+
+    def setframerate(self, framerate):
+        if self._nframeswritten:
+            raise Error('cannot change parameters after starting to write')
+        if framerate <= 0:
+            raise Error('bad frame rate')
+        self._framerate = framerate
+
+    def getframerate(self):
+        if not self._framerate:
+            raise Error('frame rate not set')
+        return self._framerate
+
+    def setnframes(self, nframes):
+        if self._nframeswritten:
+            raise Error('cannot change parameters after starting to write')
+        self._nframes = nframes
+
+    def getnframes(self):
+        return self._nframeswritten
+
+    def setcomptype(self, comptype, compname):
+        if self._nframeswritten:
+            raise Error('cannot change parameters after starting to write')
+        if comptype not in (b'NONE', b'ulaw', b'ULAW',
+                            b'alaw', b'ALAW', b'G722'):
+            raise Error('unsupported compression type')
+        self._comptype = comptype
+        self._compname = compname
+
+    def getcomptype(self):
+        return self._comptype
+
+    def getcompname(self):
+        return self._compname
+
+##  def setversion(self, version):
+##      if self._nframeswritten:
+##          raise Error, 'cannot change parameters after starting to write'
+##      self._version = version
+
+    def setparams(self, params):
+        nchannels, sampwidth, framerate, nframes, comptype, compname = params
+        if self._nframeswritten:
+            raise Error('cannot change parameters after starting to write')
+        if comptype not in (b'NONE', b'ulaw', b'ULAW',
+                            b'alaw', b'ALAW', b'G722'):
+            raise Error('unsupported compression type')
+        self.setnchannels(nchannels)
+        self.setsampwidth(sampwidth)
+        self.setframerate(framerate)
+        self.setnframes(nframes)
+        self.setcomptype(comptype, compname)
+
+    def getparams(self):
+        if not self._nchannels or not self._sampwidth or not self._framerate:
+            raise Error('not all parameters set')
+        return _aifc_params(self._nchannels, self._sampwidth, self._framerate,
+                            self._nframes, self._comptype, self._compname)
+
+    def setmark(self, id, pos, name):
+        if id <= 0:
+            raise Error('marker ID must be > 0')
+        if pos < 0:
+            raise Error('marker position must be >= 0')
+        if not isinstance(name, bytes):
+            raise Error('marker name must be bytes')
+        for i in range(len(self._markers)):
+            if id == self._markers[i][0]:
+                self._markers[i] = id, pos, name
+                return
+        self._markers.append((id, pos, name))
+
+    def getmark(self, id):
+        for marker in self._markers:
+            if id == marker[0]:
+                return marker
+        raise Error('marker {0!r} does not exist'.format(id))
+
+    def getmarkers(self):
+        if len(self._markers) == 0:
+            return None
+        return self._markers
+
+    def tell(self):
+        return self._nframeswritten
+
+    def writeframesraw(self, data):
+        if not isinstance(data, (bytes, bytearray)):
+            data = memoryview(data).cast('B')
+        self._ensure_header_written(len(data))
+        nframes = len(data) // (self._sampwidth * self._nchannels)
+        if self._convert:
+            data = self._convert(data)
+        self._file.write(data)
+        self._nframeswritten = self._nframeswritten + nframes
+        self._datawritten = self._datawritten + len(data)
+
+    def writeframes(self, data):
+        self.writeframesraw(data)
+        if self._nframeswritten != self._nframes or \
+              self._datalength != self._datawritten:
+            self._patchheader()
+
+    def close(self):
+        if self._file is None:
+            return
+        try:
+            self._ensure_header_written(0)
+            if self._datawritten & 1:
+                # quick pad to even size
+                self._file.write(b'\x00')
+                self._datawritten = self._datawritten + 1
+            self._writemarkers()
+            if self._nframeswritten != self._nframes or \
+                  self._datalength != self._datawritten or \
+                  self._marklength:
+                self._patchheader()
+        finally:
+            # Prevent ref cycles
+            self._convert = None
+            f = self._file
+            self._file = None
+            f.close()
+
+    #
+    # Internal methods.
+    #
+
+    def _lin2alaw(self, data):
+        import audioop
+        return audioop.lin2alaw(data, 2)
+
+    def _lin2ulaw(self, data):
+        import audioop
+        return audioop.lin2ulaw(data, 2)
+
+    def _lin2adpcm(self, data):
+        import audioop
+        if not hasattr(self, '_adpcmstate'):
+            self._adpcmstate = None
+        data, self._adpcmstate = audioop.lin2adpcm(data, 2, self._adpcmstate)
+        return data
+
+    def _ensure_header_written(self, datasize):
+        if not self._nframeswritten:
+            if self._comptype in (b'ULAW', b'ulaw', b'ALAW', b'alaw', b'G722'):
+                if not self._sampwidth:
+                    self._sampwidth = 2
+                if self._sampwidth != 2:
+                    raise Error('sample width must be 2 when compressing '
+                                'with ulaw/ULAW, alaw/ALAW or G7.22 (ADPCM)')
+            if not self._nchannels:
+                raise Error('# channels not specified')
+            if not self._sampwidth:
+                raise Error('sample width not specified')
+            if not self._framerate:
+                raise Error('sampling rate not specified')
+            self._write_header(datasize)
+
+    def _init_compression(self):
+        if self._comptype == b'G722':
+            self._convert = self._lin2adpcm
+        elif self._comptype in (b'ulaw', b'ULAW'):
+            self._convert = self._lin2ulaw
+        elif self._comptype in (b'alaw', b'ALAW'):
+            self._convert = self._lin2alaw
+
+    def _write_header(self, initlength):
+        if self._aifc and self._comptype != b'NONE':
+            self._init_compression()
+        self._file.write(b'FORM')
+        if not self._nframes:
+            self._nframes = initlength // (self._nchannels * self._sampwidth)
+        self._datalength = self._nframes * self._nchannels * self._sampwidth
+        if self._datalength & 1:
+            self._datalength = self._datalength + 1
+        if self._aifc:
+            if self._comptype in (b'ulaw', b'ULAW', b'alaw', b'ALAW'):
+                self._datalength = self._datalength // 2
+                if self._datalength & 1:
+                    self._datalength = self._datalength + 1
+            elif self._comptype == b'G722':
+                self._datalength = (self._datalength + 3) // 4
+                if self._datalength & 1:
+                    self._datalength = self._datalength + 1
+        try:
+            self._form_length_pos = self._file.tell()
+        except (AttributeError, OSError):
+            self._form_length_pos = None
+        commlength = self._write_form_length(self._datalength)
+        if self._aifc:
+            self._file.write(b'AIFC')
+            self._file.write(b'FVER')
+            _write_ulong(self._file, 4)
+            _write_ulong(self._file, self._version)
+        else:
+            self._file.write(b'AIFF')
+        self._file.write(b'COMM')
+        _write_ulong(self._file, commlength)
+        _write_short(self._file, self._nchannels)
+        if self._form_length_pos is not None:
+            self._nframes_pos = self._file.tell()
+        _write_ulong(self._file, self._nframes)
+        if self._comptype in (b'ULAW', b'ulaw', b'ALAW', b'alaw', b'G722'):
+            _write_short(self._file, 8)
+        else:
+            _write_short(self._file, self._sampwidth * 8)
+        _write_float(self._file, self._framerate)
+        if self._aifc:
+            self._file.write(self._comptype)
+            _write_string(self._file, self._compname)
+        self._file.write(b'SSND')
+        if self._form_length_pos is not None:
+            self._ssnd_length_pos = self._file.tell()
+        _write_ulong(self._file, self._datalength + 8)
+        _write_ulong(self._file, 0)
+        _write_ulong(self._file, 0)
+
+    def _write_form_length(self, datalength):
+        if self._aifc:
+            commlength = 18 + 5 + len(self._compname)
+            if commlength & 1:
+                commlength = commlength + 1
+            verslength = 12
+        else:
+            commlength = 18
+            verslength = 0
+        _write_ulong(self._file, 4 + verslength + self._marklength + \
+                     8 + commlength + 16 + datalength)
+        return commlength
+
+    def _patchheader(self):
+        curpos = self._file.tell()
+        if self._datawritten & 1:
+            datalength = self._datawritten + 1
+            self._file.write(b'\x00')
+        else:
+            datalength = self._datawritten
+        if datalength == self._datalength and \
+              self._nframes == self._nframeswritten and \
+              self._marklength == 0:
+            self._file.seek(curpos, 0)
+            return
+        self._file.seek(self._form_length_pos, 0)
+        dummy = self._write_form_length(datalength)
+        self._file.seek(self._nframes_pos, 0)
+        _write_ulong(self._file, self._nframeswritten)
+        self._file.seek(self._ssnd_length_pos, 0)
+        _write_ulong(self._file, datalength + 8)
+        self._file.seek(curpos, 0)
+        self._nframes = self._nframeswritten
+        self._datalength = datalength
+
+    def _writemarkers(self):
+        if len(self._markers) == 0:
+            return
+        self._file.write(b'MARK')
+        length = 2
+        for marker in self._markers:
+            id, pos, name = marker
+            length = length + len(name) + 1 + 6
+            if len(name) & 1 == 0:
+                length = length + 1
+        _write_ulong(self._file, length)
+        self._marklength = length + 8
+        _write_short(self._file, len(self._markers))
+        for marker in self._markers:
+            id, pos, name = marker
+            _write_short(self._file, id)
+            _write_ulong(self._file, pos)
+            _write_string(self._file, name)
+
+def open(f, mode=None):
+    if mode is None:
+        if hasattr(f, 'mode'):
+            mode = f.mode
+        else:
+            mode = 'rb'
+    if mode in ('r', 'rb'):
+        return Aifc_read(f)
+    elif mode in ('w', 'wb'):
+        return Aifc_write(f)
+    else:
+        raise Error("mode must be 'r', 'rb', 'w', or 'wb'")
+
+def openfp(f, mode=None):
+    warnings.warn("aifc.openfp is deprecated since Python 3.7. "
+                  "Use aifc.open instead.", DeprecationWarning, stacklevel=2)
+    return open(f, mode=mode)
+
+if __name__ == '__main__':
+    import sys
+    if not sys.argv[1:]:
+        sys.argv.append('/usr/demos/data/audio/bach.aiff')
+    fn = sys.argv[1]
+    with open(fn, 'r') as f:
+        print("Reading", fn)
+        print("nchannels =", f.getnchannels())
+        print("nframes   =", f.getnframes())
+        print("sampwidth =", f.getsampwidth())
+        print("framerate =", f.getframerate())
+        print("comptype  =", f.getcomptype())
+        print("compname  =", f.getcompname())
+        if sys.argv[2:]:
+            gn = sys.argv[2]
+            print("Writing", gn)
+            with open(gn, 'w') as g:
+                g.setparams(f.getparams())
+                while 1:
+                    data = f.readframes(1024)
+                    if not data:
+                        break
+                    g.writeframes(data)
+            print("Done.")
diff --git a/Lib/imghdr.py b/Lib/imghdr.py
new file mode 100644
index 000000000..c4a30094c
--- /dev/null
+++ b/Lib/imghdr.py
@@ -0,0 +1,171 @@
+"""Recognize image file formats based on their first few bytes."""
+
+#from os import PathLike
+
+__all__ = ["what"]
+
+# should replace using FileIO into file
+from io import FileIO
+#-------------------------#
+# Recognize image headers #
+#-------------------------#
+
+def what(file, h=None):
+    f = None
+    try:
+        if h is None:
+            # if isinstance(file, (str, PathLike))
+            if isinstance(file, str): # FIXME(corona10): RustPython doesn't support PathLike yet.
+                f = FileIO(file, 'rb')
+                h = f.read(32)
+            else:
+                location = file.tell()
+                h = file.read(32)
+                file.seek(location)
+        for tf in tests:
+            res = tf(h, f)
+            if res:
+                return res
+    finally:
+        if f: f.close()
+    return None
+
+
+#---------------------------------#
+# Subroutines per image file type #
+#---------------------------------#
+
+tests = []
+
+def test_jpeg(h, f):
+    """JPEG data in JFIF or Exif format"""
+    if h[6:10] in (b'JFIF', b'Exif'):
+        return 'jpeg'
+
+tests.append(test_jpeg)
+
+def test_png(h, f):
+    if h.startswith(b'\211PNG\r\n\032\n'):
+        return 'png'
+
+tests.append(test_png)
+
+def test_gif(h, f):
+    """GIF ('87 and '89 variants)"""
+    if h[:6] in (b'GIF87a', b'GIF89a'):
+        return 'gif'
+
+tests.append(test_gif)
+
+def test_tiff(h, f):
+    """TIFF (can be in Motorola or Intel byte order)"""
+    if h[:2] in (b'MM', b'II'):
+        return 'tiff'
+
+tests.append(test_tiff)
+
+def test_rgb(h, f):
+    """SGI image library"""
+    if h.startswith(b'\001\332'):
+        return 'rgb'
+
+tests.append(test_rgb)
+
+def test_pbm(h, f):
+    """PBM (portable bitmap)"""
+    if len(h) >= 3 and \
+        h[0] == ord(b'P') and h[1] in b'14' and h[2] in b' \t\n\r':
+        return 'pbm'
+
+tests.append(test_pbm)
+
+def test_pgm(h, f):
+    """PGM (portable graymap)"""
+    if len(h) >= 3 and \
+        h[0] == ord(b'P') and h[1] in b'25' and h[2] in b' \t\n\r':
+        return 'pgm'
+
+tests.append(test_pgm)
+
+def test_ppm(h, f):
+    """PPM (portable pixmap)"""
+    if len(h) >= 3 and \
+        h[0] == ord(b'P') and h[1] in b'36' and h[2] in b' \t\n\r':
+        return 'ppm'
+
+tests.append(test_ppm)
+
+def test_rast(h, f):
+    """Sun raster file"""
+    if h.startswith(b'\x59\xA6\x6A\x95'):
+        return 'rast'
+
+tests.append(test_rast)
+
+def test_xbm(h, f):
+    """X bitmap (X10 or X11)"""
+    if h.startswith(b'#define '):
+        return 'xbm'
+
+tests.append(test_xbm)
+
+def test_bmp(h, f):
+    if h.startswith(b'BM'):
+        return 'bmp'
+
+tests.append(test_bmp)
+
+def test_webp(h, f):
+    if h.startswith(b'RIFF') and h[8:12] == b'WEBP':
+        return 'webp'
+
+tests.append(test_webp)
+
+def test_exr(h, f):
+    if h.startswith(b'\x76\x2f\x31\x01'):
+        return 'exr'
+
+tests.append(test_exr)
+
+#--------------------#
+# Small test program #
+#--------------------#
+
+def test():
+    import sys
+    recursive = 0
+    if sys.argv[1:] and sys.argv[1] == '-r':
+        del sys.argv[1:2]
+        recursive = 1
+    try:
+        if sys.argv[1:]:
+            testall(sys.argv[1:], recursive, 1)
+        else:
+            testall(['.'], recursive, 1)
+    except KeyboardInterrupt:
+        sys.stderr.write('\n[Interrupted]\n')
+        sys.exit(1)
+
+def testall(list, recursive, toplevel):
+    import sys
+    import os
+    for filename in list:
+        if os.path.isdir(filename):
+            print(filename + '/:', end=' ')
+            if recursive or toplevel:
+                print('recursing down:')
+                import glob
+                names = glob.glob(os.path.join(filename, '*'))
+                testall(names, recursive, 0)
+            else:
+                print('*** directory (use -r) ***')
+        else:
+            print(filename + ':', end=' ')
+            sys.stdout.flush()
+            try:
+                print(what(filename))
+            except OSError:
+                print('*** not found ***')
+
+if __name__ == '__main__':
+    test()
diff --git a/Lib/runpy.py b/Lib/runpy.py
index f69b21a35..d08d53542 100644
--- a/Lib/runpy.py
+++ b/Lib/runpy.py
@@ -11,10 +11,12 @@ importers when locating support scripts as well as when importing modules.
 
 
 import sys
-import __importlib_util
+try:
+    import __importlib_util
+except ImportError:
 # FIXME replace above with below once we can import importlib
-# import importlib.machinery # importlib first so we can test #15386 via -m
-# import importlib.util
+    import importlib.machinery # importlib first so we can test #15386 via -m
+    import importlib.util as __importlib_util
 import types
 # FIXME uncomment line below once we can import pkgutil
 # from pkgutil import read_code, get_importer
diff --git a/Lib/site.py b/Lib/site.py
new file mode 100644
index 000000000..170dbc8c1
--- /dev/null
+++ b/Lib/site.py
@@ -0,0 +1,625 @@
+"""Append module search paths for third-party packages to sys.path.
+
+****************************************************************
+* This module is automatically imported during initialization. *
+****************************************************************
+
+This will append site-specific paths to the module search path.  On
+Unix (including Mac OSX), it starts with sys.prefix and
+sys.exec_prefix (if different) and appends
+lib/python<version>/site-packages.
+On other platforms (such as Windows), it tries each of the
+prefixes directly, as well as with lib/site-packages appended.  The
+resulting directories, if they exist, are appended to sys.path, and
+also inspected for path configuration files.
+
+If a file named "pyvenv.cfg" exists one directory above sys.executable,
+sys.prefix and sys.exec_prefix are set to that directory and
+it is also checked for site-packages (sys.base_prefix and
+sys.base_exec_prefix will always be the "real" prefixes of the Python
+installation). If "pyvenv.cfg" (a bootstrap configuration file) contains
+the key "include-system-site-packages" set to anything other than "false"
+(case-insensitive), the system-level prefixes will still also be
+searched for site-packages; otherwise they won't.
+
+All of the resulting site-specific directories, if they exist, are
+appended to sys.path, and also inspected for path configuration
+files.
+
+A path configuration file is a file whose name has the form
+<package>.pth; its contents are additional directories (one per line)
+to be added to sys.path.  Non-existing directories (or
+non-directories) are never added to sys.path; no directory is added to
+sys.path more than once.  Blank lines and lines beginning with
+'#' are skipped. Lines starting with 'import' are executed.
+
+For example, suppose sys.prefix and sys.exec_prefix are set to
+/usr/local and there is a directory /usr/local/lib/python2.5/site-packages
+with three subdirectories, foo, bar and spam, and two path
+configuration files, foo.pth and bar.pth.  Assume foo.pth contains the
+following:
+
+  # foo package configuration
+  foo
+  bar
+  bletch
+
+and bar.pth contains:
+
+  # bar package configuration
+  bar
+
+Then the following directories are added to sys.path, in this order:
+
+  /usr/local/lib/python2.5/site-packages/bar
+  /usr/local/lib/python2.5/site-packages/foo
+
+Note that bletch is omitted because it doesn't exist; bar precedes foo
+because bar.pth comes alphabetically before foo.pth; and spam is
+omitted because it is not mentioned in either path configuration file.
+
+The readline module is also automatically configured to enable
+completion for systems that support it.  This can be overridden in
+sitecustomize, usercustomize or PYTHONSTARTUP.  Starting Python in
+isolated mode (-I) disables automatic readline configuration.
+
+After these operations, an attempt is made to import a module
+named sitecustomize, which can perform arbitrary additional
+site-specific customizations.  If this import fails with an
+ImportError exception, it is silently ignored.
+"""
+
+import sys
+import os
+import builtins
+import _sitebuiltins
+
+# Prefixes for site-packages; add additional prefixes like /usr/local here
+PREFIXES = [sys.prefix, sys.exec_prefix]
+# Enable per user site-packages directory
+# set it to False to disable the feature or True to force the feature
+ENABLE_USER_SITE = None
+
+# for distutils.commands.install
+# These values are initialized by the getuserbase() and getusersitepackages()
+# functions, through the main() function when Python starts.
+USER_SITE = None
+USER_BASE = None
+
+
+def makepath(*paths):
+    dir = os.path.join(*paths)
+    try:
+        dir = os.path.abspath(dir)
+    except OSError:
+        pass
+    return dir, os.path.normcase(dir)
+
+
+def abs_paths():
+    """Set all module __file__ and __cached__ attributes to an absolute path"""
+    for m in set(sys.modules.values()):
+        if (getattr(getattr(m, '__loader__', None), '__module__', None) not in
+                ('_frozen_importlib', '_frozen_importlib_external')):
+            continue   # don't mess with a PEP 302-supplied __file__
+        try:
+            m.__file__ = os.path.abspath(m.__file__)
+        except (AttributeError, OSError, TypeError):
+            pass
+        try:
+            m.__cached__ = os.path.abspath(m.__cached__)
+        except (AttributeError, OSError, TypeError):
+            pass
+
+
+def removeduppaths():
+    """ Remove duplicate entries from sys.path along with making them
+    absolute"""
+    # This ensures that the initial path provided by the interpreter contains
+    # only absolute pathnames, even if we're running from the build directory.
+    L = []
+    known_paths = set()
+    for dir in sys.path:
+        # Filter out duplicate paths (on case-insensitive file systems also
+        # if they only differ in case); turn relative paths into absolute
+        # paths.
+        dir, dircase = makepath(dir)
+        if dircase not in known_paths:
+            L.append(dir)
+            known_paths.add(dircase)
+    sys.path[:] = L
+    return known_paths
+
+
+def _init_pathinfo():
+    """Return a set containing all existing file system items from sys.path."""
+    d = set()
+    for item in sys.path:
+        try:
+            if os.path.exists(item):
+                _, itemcase = makepath(item)
+                d.add(itemcase)
+        except TypeError:
+            continue
+    return d
+
+
+def addpackage(sitedir, name, known_paths):
+    """Process a .pth file within the site-packages directory:
+       For each line in the file, either combine it with sitedir to a path
+       and add that to known_paths, or execute it if it starts with 'import '.
+    """
+    if known_paths is None:
+        known_paths = _init_pathinfo()
+        reset = True
+    else:
+        reset = False
+    fullname = os.path.join(sitedir, name)
+    try:
+        f = open(fullname, "r")
+    except OSError:
+        return
+    with f:
+        for n, line in enumerate(f):
+            if line.startswith("#"):
+                continue
+            try:
+                if line.startswith(("import ", "import\t")):
+                    exec(line)
+                    continue
+                line = line.rstrip()
+                dir, dircase = makepath(sitedir, line)
+                if not dircase in known_paths and os.path.exists(dir):
+                    sys.path.append(dir)
+                    known_paths.add(dircase)
+            except Exception:
+                print("Error processing line {:d} of {}:\n".format(n+1, fullname),
+                      file=sys.stderr)
+                import traceback
+                for record in traceback.format_exception(*sys.exc_info()):
+                    for line in record.splitlines():
+                        print('  '+line, file=sys.stderr)
+                print("\nRemainder of file ignored", file=sys.stderr)
+                break
+    if reset:
+        known_paths = None
+    return known_paths
+
+
+def addsitedir(sitedir, known_paths=None):
+    """Add 'sitedir' argument to sys.path if missing and handle .pth files in
+    'sitedir'"""
+    if known_paths is None:
+        known_paths = _init_pathinfo()
+        reset = True
+    else:
+        reset = False
+    sitedir, sitedircase = makepath(sitedir)
+    if not sitedircase in known_paths:
+        sys.path.append(sitedir)        # Add path component
+        known_paths.add(sitedircase)
+    try:
+        names = os.listdir(sitedir)
+    except OSError:
+        return
+    names = [name for name in names if name.endswith(".pth")]
+    for name in sorted(names):
+        addpackage(sitedir, name, known_paths)
+    if reset:
+        known_paths = None
+    return known_paths
+
+
+def check_enableusersite():
+    """Check if user site directory is safe for inclusion
+
+    The function tests for the command line flag (including environment var),
+    process uid/gid equal to effective uid/gid.
+
+    None: Disabled for security reasons
+    False: Disabled by user (command line option)
+    True: Safe and enabled
+    """
+    if sys.flags.no_user_site:
+        return False
+
+    if hasattr(os, "getuid") and hasattr(os, "geteuid"):
+        # check process uid == effective uid
+        if os.geteuid() != os.getuid():
+            return None
+    if hasattr(os, "getgid") and hasattr(os, "getegid"):
+        # check process gid == effective gid
+        if os.getegid() != os.getgid():
+            return None
+
+    return True
+
+
+# NOTE: sysconfig and it's dependencies are relatively large but site module
+# needs very limited part of them.
+# To speedup startup time, we have copy of them.
+#
+# See https://bugs.python.org/issue29585
+
+# Copy of sysconfig._getuserbase()
+def _getuserbase():
+    env_base = os.environ.get("PYTHONUSERBASE", None)
+    if env_base:
+        return env_base
+
+    def joinuser(*args):
+        return os.path.expanduser(os.path.join(*args))
+
+    if os.name == "nt":
+        base = os.environ.get("APPDATA") or "~"
+        return joinuser(base, "Python")
+
+    if sys.platform == "darwin" and sys._framework:
+        return joinuser("~", "Library", sys._framework,
+                        "%d.%d" % sys.version_info[:2])
+
+    return joinuser("~", ".local")
+
+
+# Same to sysconfig.get_path('purelib', os.name+'_user')
+def _get_path(userbase):
+    version = sys.version_info
+
+    if os.name == 'nt':
+        return f'{userbase}\\Python{version[0]}{version[1]}\\site-packages'
+
+    if sys.platform == 'darwin' and sys._framework:
+        return f'{userbase}/lib/python/site-packages'
+
+    return f'{userbase}/lib/python{version[0]}.{version[1]}/site-packages'
+
+
+def getuserbase():
+    """Returns the `user base` directory path.
+
+    The `user base` directory can be used to store data. If the global
+    variable ``USER_BASE`` is not initialized yet, this function will also set
+    it.
+    """
+    global USER_BASE
+    if USER_BASE is None:
+        USER_BASE = _getuserbase()
+    return USER_BASE
+
+
+def getusersitepackages():
+    """Returns the user-specific site-packages directory path.
+
+    If the global variable ``USER_SITE`` is not initialized yet, this
+    function will also set it.
+    """
+    global USER_SITE
+    userbase = getuserbase() # this will also set USER_BASE
+
+    if USER_SITE is None:
+        USER_SITE = _get_path(userbase)
+
+    return USER_SITE
+
+def addusersitepackages(known_paths):
+    """Add a per user site-package to sys.path
+
+    Each user has its own python directory with site-packages in the
+    home directory.
+    """
+    # get the per user site-package path
+    # this call will also make sure USER_BASE and USER_SITE are set
+    user_site = getusersitepackages()
+
+    if ENABLE_USER_SITE and os.path.isdir(user_site):
+        addsitedir(user_site, known_paths)
+    return known_paths
+
+def getsitepackages(prefixes=None):
+    """Returns a list containing all global site-packages directories.
+
+    For each directory present in ``prefixes`` (or the global ``PREFIXES``),
+    this function will find its `site-packages` subdirectory depending on the
+    system environment, and will return a list of full paths.
+    """
+    sitepackages = []
+    seen = set()
+
+    if prefixes is None:
+        prefixes = PREFIXES
+
+    for prefix in prefixes:
+        if not prefix or prefix in seen:
+            continue
+        seen.add(prefix)
+
+        if os.sep == '/':
+            sitepackages.append(os.path.join(prefix, "lib",
+                                        # XXX changed for RustPython
+                                        "rustpython%d.%d" % sys.version_info[:2],
+                                        "site-packages"))
+        else:
+            sitepackages.append(prefix)
+            sitepackages.append(os.path.join(prefix, "lib", "site-packages"))
+    return sitepackages
+
+def addsitepackages(known_paths, prefixes=None):
+    """Add site-packages to sys.path"""
+    for sitedir in getsitepackages(prefixes):
+        if os.path.isdir(sitedir):
+            addsitedir(sitedir, known_paths)
+
+    return known_paths
+
+def setquit():
+    """Define new builtins 'quit' and 'exit'.
+
+    These are objects which make the interpreter exit when called.
+    The repr of each object contains a hint at how it works.
+
+    """
+    if os.sep == '\\':
+        eof = 'Ctrl-Z plus Return'
+    else:
+        eof = 'Ctrl-D (i.e. EOF)'
+
+    builtins.quit = _sitebuiltins.Quitter('quit', eof)
+    builtins.exit = _sitebuiltins.Quitter('exit', eof)
+
+
+def setcopyright():
+    """Set 'copyright' and 'credits' in builtins"""
+    builtins.copyright = _sitebuiltins._Printer("copyright", sys.copyright)
+    if sys.platform[:4] == 'java':
+        builtins.credits = _sitebuiltins._Printer(
+            "credits",
+            "Jython is maintained by the Jython developers (www.jython.org).")
+    else:
+        builtins.credits = _sitebuiltins._Printer("credits", """\
+    Thanks to CWI, CNRI, BeOpen.com, Zope Corporation and a cast of thousands
+    for supporting Python development.  See www.python.org for more information.""")
+    files, dirs = [], []
+    # Not all modules are required to have a __file__ attribute.  See
+    # PEP 420 for more details.
+    if hasattr(os, '__file__'):
+        here = os.path.dirname(os.__file__)
+        files.extend(["LICENSE.txt", "LICENSE"])
+        dirs.extend([os.path.join(here, os.pardir), here, os.curdir])
+    builtins.license = _sitebuiltins._Printer(
+        "license",
+        "See https://www.python.org/psf/license/",
+        files, dirs)
+
+
+def sethelper():
+    builtins.help = _sitebuiltins._Helper()
+
+def enablerlcompleter():
+    """Enable default readline configuration on interactive prompts, by
+    registering a sys.__interactivehook__.
+
+    If the readline module can be imported, the hook will set the Tab key
+    as completion key and register ~/.python_history as history file.
+    This can be overridden in the sitecustomize or usercustomize module,
+    or in a PYTHONSTARTUP file.
+    """
+    def register_readline():
+        import atexit
+        try:
+            import readline
+            import rlcompleter
+        except ImportError:
+            return
+
+        # Reading the initialization (config) file may not be enough to set a
+        # completion key, so we set one first and then read the file.
+        readline_doc = getattr(readline, '__doc__', '')
+        if readline_doc is not None and 'libedit' in readline_doc:
+            readline.parse_and_bind('bind ^I rl_complete')
+        else:
+            readline.parse_and_bind('tab: complete')
+
+        try:
+            readline.read_init_file()
+        except OSError:
+            # An OSError here could have many causes, but the most likely one
+            # is that there's no .inputrc file (or .editrc file in the case of
+            # Mac OS X + libedit) in the expected location.  In that case, we
+            # want to ignore the exception.
+            pass
+
+        if readline.get_current_history_length() == 0:
+            # If no history was loaded, default to .python_history.
+            # The guard is necessary to avoid doubling history size at
+            # each interpreter exit when readline was already configured
+            # through a PYTHONSTARTUP hook, see:
+            # http://bugs.python.org/issue5845#msg198636
+            history = os.path.join(os.path.expanduser('~'),
+                                   '.python_history')
+            try:
+                readline.read_history_file(history)
+            except OSError:
+                pass
+            atexit.register(readline.write_history_file, history)
+
+    sys.__interactivehook__ = register_readline
+
+def venv(known_paths):
+    global PREFIXES, ENABLE_USER_SITE
+
+    env = os.environ
+    if sys.platform == 'darwin' and '__PYVENV_LAUNCHER__' in env:
+        executable = os.environ['__PYVENV_LAUNCHER__']
+    else:
+        executable = sys.executable
+    exe_dir, _ = os.path.split(os.path.abspath(executable))
+    site_prefix = os.path.dirname(exe_dir)
+    sys._home = None
+    conf_basename = 'pyvenv.cfg'
+    candidate_confs = [
+        conffile for conffile in (
+            os.path.join(exe_dir, conf_basename),
+            os.path.join(site_prefix, conf_basename)
+            )
+        if os.path.isfile(conffile)
+        ]
+
+    if candidate_confs:
+        virtual_conf = candidate_confs[0]
+        system_site = "true"
+        # Issue 25185: Use UTF-8, as that's what the venv module uses when
+        # writing the file.
+        with open(virtual_conf, encoding='utf-8') as f:
+            for line in f:
+                if '=' in line:
+                    key, _, value = line.partition('=')
+                    key = key.strip().lower()
+                    value = value.strip()
+                    if key == 'include-system-site-packages':
+                        system_site = value.lower()
+                    elif key == 'home':
+                        sys._home = value
+
+        sys.prefix = sys.exec_prefix = site_prefix
+
+        # Doing this here ensures venv takes precedence over user-site
+        addsitepackages(known_paths, [sys.prefix])
+
+        # addsitepackages will process site_prefix again if its in PREFIXES,
+        # but that's ok; known_paths will prevent anything being added twice
+        if system_site == "true":
+            PREFIXES.insert(0, sys.prefix)
+        else:
+            PREFIXES = [sys.prefix]
+            ENABLE_USER_SITE = False
+
+    return known_paths
+
+
+def execsitecustomize():
+    """Run custom site specific code, if available."""
+    try:
+        try:
+            import sitecustomize
+        except ImportError as exc:
+            if exc.name == 'sitecustomize':
+                pass
+            else:
+                raise
+    except Exception as err:
+        if sys.flags.verbose:
+            sys.excepthook(*sys.exc_info())
+        else:
+            sys.stderr.write(
+                "Error in sitecustomize; set PYTHONVERBOSE for traceback:\n"
+                "%s: %s\n" %
+                (err.__class__.__name__, err))
+
+
+def execusercustomize():
+    """Run custom user specific code, if available."""
+    try:
+        try:
+            import usercustomize
+        except ImportError as exc:
+            if exc.name == 'usercustomize':
+                pass
+            else:
+                raise
+    except Exception as err:
+        if sys.flags.verbose:
+            sys.excepthook(*sys.exc_info())
+        else:
+            sys.stderr.write(
+                "Error in usercustomize; set PYTHONVERBOSE for traceback:\n"
+                "%s: %s\n" %
+                (err.__class__.__name__, err))
+
+
+def main():
+    """Add standard site-specific directories to the module search path.
+
+    This function is called automatically when this module is imported,
+    unless the python interpreter was started with the -S flag.
+    """
+    global ENABLE_USER_SITE
+
+    orig_path = sys.path[:]
+    known_paths = removeduppaths()
+    if orig_path != sys.path:
+        # removeduppaths() might make sys.path absolute.
+        # fix __file__ and __cached__ of already imported modules too.
+        abs_paths()
+
+    known_paths = venv(known_paths)
+    if ENABLE_USER_SITE is None:
+        ENABLE_USER_SITE = check_enableusersite()
+    known_paths = addusersitepackages(known_paths)
+    known_paths = addsitepackages(known_paths)
+    setquit()
+    setcopyright()
+    sethelper()
+    if not sys.flags.isolated:
+        enablerlcompleter()
+    execsitecustomize()
+    if ENABLE_USER_SITE:
+        execusercustomize()
+
+# Prevent extending of sys.path when python was started with -S and
+# site is imported later.
+if not sys.flags.no_site:
+    main()
+
+def _script():
+    help = """\
+    %s [--user-base] [--user-site]
+
+    Without arguments print some useful information
+    With arguments print the value of USER_BASE and/or USER_SITE separated
+    by '%s'.
+
+    Exit codes with --user-base or --user-site:
+      0 - user site directory is enabled
+      1 - user site directory is disabled by user
+      2 - uses site directory is disabled by super user
+          or for security reasons
+     >2 - unknown error
+    """
+    args = sys.argv[1:]
+    if not args:
+        user_base = getuserbase()
+        user_site = getusersitepackages()
+        print("sys.path = [")
+        for dir in sys.path:
+            print("    %r," % (dir,))
+        print("]")
+        print("USER_BASE: %r (%s)" % (user_base,
+            "exists" if os.path.isdir(user_base) else "doesn't exist"))
+        print("USER_SITE: %r (%s)" % (user_site,
+            "exists" if os.path.isdir(user_site) else "doesn't exist"))
+        print("ENABLE_USER_SITE: %r" %  ENABLE_USER_SITE)
+        sys.exit(0)
+
+    buffer = []
+    if '--user-base' in args:
+        buffer.append(USER_BASE)
+    if '--user-site' in args:
+        buffer.append(USER_SITE)
+
+    if buffer:
+        print(os.pathsep.join(buffer))
+        if ENABLE_USER_SITE:
+            sys.exit(0)
+        elif ENABLE_USER_SITE is False:
+            sys.exit(1)
+        elif ENABLE_USER_SITE is None:
+            sys.exit(2)
+        else:
+            sys.exit(3)
+    else:
+        import textwrap
+        print(textwrap.dedent(help % (sys.argv[0], os.pathsep)))
+        sys.exit(10)
+
+if __name__ == '__main__':
+    _script()
diff --git a/Lib/sndhdr.py b/Lib/sndhdr.py
new file mode 100644
index 000000000..594353136
--- /dev/null
+++ b/Lib/sndhdr.py
@@ -0,0 +1,257 @@
+"""Routines to help recognizing sound files.
+
+Function whathdr() recognizes various types of sound file headers.
+It understands almost all headers that SOX can decode.
+
+The return tuple contains the following items, in this order:
+- file type (as SOX understands it)
+- sampling rate (0 if unknown or hard to decode)
+- number of channels (0 if unknown or hard to decode)
+- number of frames in the file (-1 if unknown or hard to decode)
+- number of bits/sample, or 'U' for U-LAW, or 'A' for A-LAW
+
+If the file doesn't have a recognizable type, it returns None.
+If the file can't be opened, OSError is raised.
+
+To compute the total time, divide the number of frames by the
+sampling rate (a frame contains a sample for each channel).
+
+Function what() calls whathdr().  (It used to also use some
+heuristics for raw data, but this doesn't work very well.)
+
+Finally, the function test() is a simple main program that calls
+what() for all files mentioned on the argument list.  For directory
+arguments it calls what() for all files in that directory.  Default
+argument is "." (testing all files in the current directory).  The
+option -r tells it to recurse down directories found inside
+explicitly given directories.
+"""
+
+# The file structure is top-down except that the test program and its
+# subroutine come last.
+
+__all__ = ['what', 'whathdr']
+
+from collections import namedtuple
+
+SndHeaders = namedtuple('SndHeaders',
+                        'filetype framerate nchannels nframes sampwidth')
+
+SndHeaders.filetype.__doc__ = ("""The value for type indicates the data type
+and will be one of the strings 'aifc', 'aiff', 'au','hcom',
+'sndr', 'sndt', 'voc', 'wav', '8svx', 'sb', 'ub', or 'ul'.""")
+SndHeaders.framerate.__doc__ = ("""The sampling_rate will be either the actual
+value or 0 if unknown or difficult to decode.""")
+SndHeaders.nchannels.__doc__ = ("""The number of channels or 0 if it cannot be
+determined or if the value is difficult to decode.""")
+SndHeaders.nframes.__doc__ = ("""The value for frames will be either the number
+of frames or -1.""")
+SndHeaders.sampwidth.__doc__ = ("""Either the sample size in bits or
+'A' for A-LAW or 'U' for u-LAW.""")
+
+def what(filename):
+    """Guess the type of a sound file."""
+    res = whathdr(filename)
+    return res
+
+
+def whathdr(filename):
+    """Recognize sound headers."""
+    with open(filename, 'rb') as f:
+        h = f.read(512)
+        for tf in tests:
+            res = tf(h, f)
+            if res:
+                return SndHeaders(*res)
+        return None
+
+
+#-----------------------------------#
+# Subroutines per sound header type #
+#-----------------------------------#
+
+tests = []
+
+def test_aifc(h, f):
+    import aifc
+    if not h.startswith(b'FORM'):
+        return None
+    if h[8:12] == b'AIFC':
+        fmt = 'aifc'
+    elif h[8:12] == b'AIFF':
+        fmt = 'aiff'
+    else:
+        return None
+    f.seek(0)
+    try:
+        a = aifc.open(f, 'r')
+    except (EOFError, aifc.Error):
+        return None
+    return (fmt, a.getframerate(), a.getnchannels(),
+            a.getnframes(), 8 * a.getsampwidth())
+
+tests.append(test_aifc)
+
+
+def test_au(h, f):
+    if h.startswith(b'.snd'):
+        func = get_long_be
+    elif h[:4] in (b'\0ds.', b'dns.'):
+        func = get_long_le
+    else:
+        return None
+    filetype = 'au'
+    hdr_size = func(h[4:8])
+    data_size = func(h[8:12])
+    encoding = func(h[12:16])
+    rate = func(h[16:20])
+    nchannels = func(h[20:24])
+    sample_size = 1 # default
+    if encoding == 1:
+        sample_bits = 'U'
+    elif encoding == 2:
+        sample_bits = 8
+    elif encoding == 3:
+        sample_bits = 16
+        sample_size = 2
+    else:
+        sample_bits = '?'
+    frame_size = sample_size * nchannels
+    if frame_size:
+        nframe = data_size / frame_size
+    else:
+        nframe = -1
+    return filetype, rate, nchannels, nframe, sample_bits
+
+tests.append(test_au)
+
+
+def test_hcom(h, f):
+    if h[65:69] != b'FSSD' or h[128:132] != b'HCOM':
+        return None
+    divisor = get_long_be(h[144:148])
+    if divisor:
+        rate = 22050 / divisor
+    else:
+        rate = 0
+    return 'hcom', rate, 1, -1, 8
+
+tests.append(test_hcom)
+
+
+def test_voc(h, f):
+    if not h.startswith(b'Creative Voice File\032'):
+        return None
+    sbseek = get_short_le(h[20:22])
+    rate = 0
+    if 0 <= sbseek < 500 and h[sbseek] == 1:
+        ratecode = 256 - h[sbseek+4]
+        if ratecode:
+            rate = int(1000000.0 / ratecode)
+    return 'voc', rate, 1, -1, 8
+
+tests.append(test_voc)
+
+
+def test_wav(h, f):
+    import wave
+    # 'RIFF' <len> 'WAVE' 'fmt ' <len>
+    if not h.startswith(b'RIFF') or h[8:12] != b'WAVE' or h[12:16] != b'fmt ':
+        return None
+    f.seek(0)
+    try:
+        w = wave.open(f, 'r')
+    except (EOFError, wave.Error):
+        return None
+    return ('wav', w.getframerate(), w.getnchannels(),
+                   w.getnframes(), 8*w.getsampwidth())
+
+tests.append(test_wav)
+
+
+def test_8svx(h, f):
+    if not h.startswith(b'FORM') or h[8:12] != b'8SVX':
+        return None
+    # Should decode it to get #channels -- assume always 1
+    return '8svx', 0, 1, 0, 8
+
+tests.append(test_8svx)
+
+
+def test_sndt(h, f):
+    if h.startswith(b'SOUND'):
+        nsamples = get_long_le(h[8:12])
+        rate = get_short_le(h[20:22])
+        return 'sndt', rate, 1, nsamples, 8
+
+tests.append(test_sndt)
+
+
+def test_sndr(h, f):
+    if h.startswith(b'\0\0'):
+        rate = get_short_le(h[2:4])
+        if 4000 <= rate <= 25000:
+            return 'sndr', rate, 1, -1, 8
+
+tests.append(test_sndr)
+
+
+#-------------------------------------------#
+# Subroutines to extract numbers from bytes #
+#-------------------------------------------#
+
+def get_long_be(b):
+    return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | b[3]
+
+def get_long_le(b):
+    return (b[3] << 24) | (b[2] << 16) | (b[1] << 8) | b[0]
+
+def get_short_be(b):
+    return (b[0] << 8) | b[1]
+
+def get_short_le(b):
+    return (b[1] << 8) | b[0]
+
+
+#--------------------#
+# Small test program #
+#--------------------#
+
+def test():
+    import sys
+    recursive = 0
+    if sys.argv[1:] and sys.argv[1] == '-r':
+        del sys.argv[1:2]
+        recursive = 1
+    try:
+        if sys.argv[1:]:
+            testall(sys.argv[1:], recursive, 1)
+        else:
+            testall(['.'], recursive, 1)
+    except KeyboardInterrupt:
+        sys.stderr.write('\n[Interrupted]\n')
+        sys.exit(1)
+
+def testall(list, recursive, toplevel):
+    import sys
+    import os
+    for filename in list:
+        if os.path.isdir(filename):
+            print(filename + '/:', end=' ')
+            if recursive or toplevel:
+                print('recursing down:')
+                import glob
+                names = glob.glob(os.path.join(filename, '*'))
+                testall(names, recursive, 0)
+            else:
+                print('*** directory (use -r) ***')
+        else:
+            print(filename + ':', end=' ')
+            sys.stdout.flush()
+            try:
+                print(what(filename))
+            except OSError:
+                print('*** not found ***')
+
+if __name__ == '__main__':
+    test()
diff --git a/Lib/sunau.py b/Lib/sunau.py
new file mode 100644
index 000000000..129502b0b
--- /dev/null
+++ b/Lib/sunau.py
@@ -0,0 +1,531 @@
+"""Stuff to parse Sun and NeXT audio files.
+
+An audio file consists of a header followed by the data.  The structure
+of the header is as follows.
+
+        +---------------+
+        | magic word    |
+        +---------------+
+        | header size   |
+        +---------------+
+        | data size     |
+        +---------------+
+        | encoding      |
+        +---------------+
+        | sample rate   |
+        +---------------+
+        | # of channels |
+        +---------------+
+        | info          |
+        |               |
+        +---------------+
+
+The magic word consists of the 4 characters '.snd'.  Apart from the
+info field, all header fields are 4 bytes in size.  They are all
+32-bit unsigned integers encoded in big-endian byte order.
+
+The header size really gives the start of the data.
+The data size is the physical size of the data.  From the other
+parameters the number of frames can be calculated.
+The encoding gives the way in which audio samples are encoded.
+Possible values are listed below.
+The info field currently consists of an ASCII string giving a
+human-readable description of the audio file.  The info field is
+padded with NUL bytes to the header size.
+
+Usage.
+
+Reading audio files:
+        f = sunau.open(file, 'r')
+where file is either the name of a file or an open file pointer.
+The open file pointer must have methods read(), seek(), and close().
+When the setpos() and rewind() methods are not used, the seek()
+method is not  necessary.
+
+This returns an instance of a class with the following public methods:
+        getnchannels()  -- returns number of audio channels (1 for
+                           mono, 2 for stereo)
+        getsampwidth()  -- returns sample width in bytes
+        getframerate()  -- returns sampling frequency
+        getnframes()    -- returns number of audio frames
+        getcomptype()   -- returns compression type ('NONE' or 'ULAW')
+        getcompname()   -- returns human-readable version of
+                           compression type ('not compressed' matches 'NONE')
+        getparams()     -- returns a namedtuple consisting of all of the
+                           above in the above order
+        getmarkers()    -- returns None (for compatibility with the
+                           aifc module)
+        getmark(id)     -- raises an error since the mark does not
+                           exist (for compatibility with the aifc module)
+        readframes(n)   -- returns at most n frames of audio
+        rewind()        -- rewind to the beginning of the audio stream
+        setpos(pos)     -- seek to the specified position
+        tell()          -- return the current position
+        close()         -- close the instance (make it unusable)
+The position returned by tell() and the position given to setpos()
+are compatible and have nothing to do with the actual position in the
+file.
+The close() method is called automatically when the class instance
+is destroyed.
+
+Writing audio files:
+        f = sunau.open(file, 'w')
+where file is either the name of a file or an open file pointer.
+The open file pointer must have methods write(), tell(), seek(), and
+close().
+
+This returns an instance of a class with the following public methods:
+        setnchannels(n) -- set the number of channels
+        setsampwidth(n) -- set the sample width
+        setframerate(n) -- set the frame rate
+        setnframes(n)   -- set the number of frames
+        setcomptype(type, name)
+                        -- set the compression type and the
+                           human-readable compression type
+        setparams(tuple)-- set all parameters at once
+        tell()          -- return current position in output file
+        writeframesraw(data)
+                        -- write audio frames without pathing up the
+                           file header
+        writeframes(data)
+                        -- write audio frames and patch up the file header
+        close()         -- patch up the file header and close the
+                           output file
+You should set the parameters before the first writeframesraw or
+writeframes.  The total number of frames does not need to be set,
+but when it is set to the correct value, the header does not have to
+be patched up.
+It is best to first set all parameters, perhaps possibly the
+compression type, and then write audio frames using writeframesraw.
+When all frames have been written, either call writeframes(b'') or
+close() to patch up the sizes in the header.
+The close() method is called automatically when the class instance
+is destroyed.
+"""
+
+from collections import namedtuple
+import warnings
+
+_sunau_params = namedtuple('_sunau_params',
+                           'nchannels sampwidth framerate nframes comptype compname')
+
+# from <multimedia/audio_filehdr.h>
+AUDIO_FILE_MAGIC = 0x2e736e64
+AUDIO_FILE_ENCODING_MULAW_8 = 1
+AUDIO_FILE_ENCODING_LINEAR_8 = 2
+AUDIO_FILE_ENCODING_LINEAR_16 = 3
+AUDIO_FILE_ENCODING_LINEAR_24 = 4
+AUDIO_FILE_ENCODING_LINEAR_32 = 5
+AUDIO_FILE_ENCODING_FLOAT = 6
+AUDIO_FILE_ENCODING_DOUBLE = 7
+AUDIO_FILE_ENCODING_ADPCM_G721 = 23
+AUDIO_FILE_ENCODING_ADPCM_G722 = 24
+AUDIO_FILE_ENCODING_ADPCM_G723_3 = 25
+AUDIO_FILE_ENCODING_ADPCM_G723_5 = 26
+AUDIO_FILE_ENCODING_ALAW_8 = 27
+
+# from <multimedia/audio_hdr.h>
+AUDIO_UNKNOWN_SIZE = 0xFFFFFFFF        # ((unsigned)(~0))
+
+_simple_encodings = [AUDIO_FILE_ENCODING_MULAW_8,
+                     AUDIO_FILE_ENCODING_LINEAR_8,
+                     AUDIO_FILE_ENCODING_LINEAR_16,
+                     AUDIO_FILE_ENCODING_LINEAR_24,
+                     AUDIO_FILE_ENCODING_LINEAR_32,
+                     AUDIO_FILE_ENCODING_ALAW_8]
+
+class Error(Exception):
+    pass
+
+def _read_u32(file):
+    x = 0
+    for i in range(4):
+        byte = file.read(1)
+        if not byte:
+            raise EOFError
+        x = x*256 + ord(byte)
+    return x
+
+def _write_u32(file, x):
+    data = []
+    for i in range(4):
+        d, m = divmod(x, 256)
+        data.insert(0, int(m))
+        x = d
+    file.write(bytes(data))
+
+class Au_read:
+
+    def __init__(self, f):
+        if type(f) == type(''):
+            import builtins
+            f = builtins.open(f, 'rb')
+            self._opened = True
+        else:
+            self._opened = False
+        self.initfp(f)
+
+    def __del__(self):
+        if self._file:
+            self.close()
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        self.close()
+
+    def initfp(self, file):
+        self._file = file
+        self._soundpos = 0
+        magic = int(_read_u32(file))
+        if magic != AUDIO_FILE_MAGIC:
+            raise Error('bad magic number')
+        self._hdr_size = int(_read_u32(file))
+        if self._hdr_size < 24:
+            raise Error('header size too small')
+        if self._hdr_size > 100:
+            raise Error('header size ridiculously large')
+        self._data_size = _read_u32(file)
+        if self._data_size != AUDIO_UNKNOWN_SIZE:
+            self._data_size = int(self._data_size)
+        self._encoding = int(_read_u32(file))
+        if self._encoding not in _simple_encodings:
+            raise Error('encoding not (yet) supported')
+        if self._encoding in (AUDIO_FILE_ENCODING_MULAW_8,
+                  AUDIO_FILE_ENCODING_ALAW_8):
+            self._sampwidth = 2
+            self._framesize = 1
+        elif self._encoding == AUDIO_FILE_ENCODING_LINEAR_8:
+            self._framesize = self._sampwidth = 1
+        elif self._encoding == AUDIO_FILE_ENCODING_LINEAR_16:
+            self._framesize = self._sampwidth = 2
+        elif self._encoding == AUDIO_FILE_ENCODING_LINEAR_24:
+            self._framesize = self._sampwidth = 3
+        elif self._encoding == AUDIO_FILE_ENCODING_LINEAR_32:
+            self._framesize = self._sampwidth = 4
+        else:
+            raise Error('unknown encoding')
+        self._framerate = int(_read_u32(file))
+        self._nchannels = int(_read_u32(file))
+        if not self._nchannels:
+            raise Error('bad # of channels')
+        self._framesize = self._framesize * self._nchannels
+        if self._hdr_size > 24:
+            self._info = file.read(self._hdr_size - 24)
+            self._info, _, _ = self._info.partition(b'\0')
+        else:
+            self._info = b''
+        try:
+            self._data_pos = file.tell()
+        except (AttributeError, OSError):
+            self._data_pos = None
+
+    def getfp(self):
+        return self._file
+
+    def getnchannels(self):
+        return self._nchannels
+
+    def getsampwidth(self):
+        return self._sampwidth
+
+    def getframerate(self):
+        return self._framerate
+
+    def getnframes(self):
+        if self._data_size == AUDIO_UNKNOWN_SIZE:
+            return AUDIO_UNKNOWN_SIZE
+        if self._encoding in _simple_encodings:
+            return self._data_size // self._framesize
+        return 0                # XXX--must do some arithmetic here
+
+    def getcomptype(self):
+        if self._encoding == AUDIO_FILE_ENCODING_MULAW_8:
+            return 'ULAW'
+        elif self._encoding == AUDIO_FILE_ENCODING_ALAW_8:
+            return 'ALAW'
+        else:
+            return 'NONE'
+
+    def getcompname(self):
+        if self._encoding == AUDIO_FILE_ENCODING_MULAW_8:
+            return 'CCITT G.711 u-law'
+        elif self._encoding == AUDIO_FILE_ENCODING_ALAW_8:
+            return 'CCITT G.711 A-law'
+        else:
+            return 'not compressed'
+
+    def getparams(self):
+        return _sunau_params(self.getnchannels(), self.getsampwidth(),
+                  self.getframerate(), self.getnframes(),
+                  self.getcomptype(), self.getcompname())
+
+    def getmarkers(self):
+        return None
+
+    def getmark(self, id):
+        raise Error('no marks')
+
+    def readframes(self, nframes):
+        if self._encoding in _simple_encodings:
+            if nframes == AUDIO_UNKNOWN_SIZE:
+                data = self._file.read()
+            else:
+                data = self._file.read(nframes * self._framesize)
+            self._soundpos += len(data) // self._framesize
+            if self._encoding == AUDIO_FILE_ENCODING_MULAW_8:
+                import audioop
+                data = audioop.ulaw2lin(data, self._sampwidth)
+            return data
+        return None             # XXX--not implemented yet
+
+    def rewind(self):
+        if self._data_pos is None:
+            raise OSError('cannot seek')
+        self._file.seek(self._data_pos)
+        self._soundpos = 0
+
+    def tell(self):
+        return self._soundpos
+
+    def setpos(self, pos):
+        if pos < 0 or pos > self.getnframes():
+            raise Error('position not in range')
+        if self._data_pos is None:
+            raise OSError('cannot seek')
+        self._file.seek(self._data_pos + pos * self._framesize)
+        self._soundpos = pos
+
+    def close(self):
+        file = self._file
+        if file:
+            self._file = None
+            if self._opened:
+                file.close()
+
+class Au_write:
+
+    def __init__(self, f):
+        if type(f) == type(''):
+            import builtins
+            f = builtins.open(f, 'wb')
+            self._opened = True
+        else:
+            self._opened = False
+        self.initfp(f)
+
+    def __del__(self):
+        if self._file:
+            self.close()
+        self._file = None
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        self.close()
+
+    def initfp(self, file):
+        self._file = file
+        self._framerate = 0
+        self._nchannels = 0
+        self._sampwidth = 0
+        self._framesize = 0
+        self._nframes = AUDIO_UNKNOWN_SIZE
+        self._nframeswritten = 0
+        self._datawritten = 0
+        self._datalength = 0
+        self._info = b''
+        self._comptype = 'ULAW' # default is U-law
+
+    def setnchannels(self, nchannels):
+        if self._nframeswritten:
+            raise Error('cannot change parameters after starting to write')
+        if nchannels not in (1, 2, 4):
+            raise Error('only 1, 2, or 4 channels supported')
+        self._nchannels = nchannels
+
+    def getnchannels(self):
+        if not self._nchannels:
+            raise Error('number of channels not set')
+        return self._nchannels
+
+    def setsampwidth(self, sampwidth):
+        if self._nframeswritten:
+            raise Error('cannot change parameters after starting to write')
+        if sampwidth not in (1, 2, 3, 4):
+            raise Error('bad sample width')
+        self._sampwidth = sampwidth
+
+    def getsampwidth(self):
+        if not self._framerate:
+            raise Error('sample width not specified')
+        return self._sampwidth
+
+    def setframerate(self, framerate):
+        if self._nframeswritten:
+            raise Error('cannot change parameters after starting to write')
+        self._framerate = framerate
+
+    def getframerate(self):
+        if not self._framerate:
+            raise Error('frame rate not set')
+        return self._framerate
+
+    def setnframes(self, nframes):
+        if self._nframeswritten:
+            raise Error('cannot change parameters after starting to write')
+        if nframes < 0:
+            raise Error('# of frames cannot be negative')
+        self._nframes = nframes
+
+    def getnframes(self):
+        return self._nframeswritten
+
+    def setcomptype(self, type, name):
+        if type in ('NONE', 'ULAW'):
+            self._comptype = type
+        else:
+            raise Error('unknown compression type')
+
+    def getcomptype(self):
+        return self._comptype
+
+    def getcompname(self):
+        if self._comptype == 'ULAW':
+            return 'CCITT G.711 u-law'
+        elif self._comptype == 'ALAW':
+            return 'CCITT G.711 A-law'
+        else:
+            return 'not compressed'
+
+    def setparams(self, params):
+        nchannels, sampwidth, framerate, nframes, comptype, compname = params
+        self.setnchannels(nchannels)
+        self.setsampwidth(sampwidth)
+        self.setframerate(framerate)
+        self.setnframes(nframes)
+        self.setcomptype(comptype, compname)
+
+    def getparams(self):
+        return _sunau_params(self.getnchannels(), self.getsampwidth(),
+                  self.getframerate(), self.getnframes(),
+                  self.getcomptype(), self.getcompname())
+
+    def tell(self):
+        return self._nframeswritten
+
+    def writeframesraw(self, data):
+        if not isinstance(data, (bytes, bytearray)):
+            data = memoryview(data).cast('B')
+        self._ensure_header_written()
+        if self._comptype == 'ULAW':
+            import audioop
+            data = audioop.lin2ulaw(data, self._sampwidth)
+        nframes = len(data) // self._framesize
+        self._file.write(data)
+        self._nframeswritten = self._nframeswritten + nframes
+        self._datawritten = self._datawritten + len(data)
+
+    def writeframes(self, data):
+        self.writeframesraw(data)
+        if self._nframeswritten != self._nframes or \
+                  self._datalength != self._datawritten:
+            self._patchheader()
+
+    def close(self):
+        if self._file:
+            try:
+                self._ensure_header_written()
+                if self._nframeswritten != self._nframes or \
+                        self._datalength != self._datawritten:
+                    self._patchheader()
+                self._file.flush()
+            finally:
+                file = self._file
+                self._file = None
+                if self._opened:
+                    file.close()
+
+    #
+    # private methods
+    #
+
+    def _ensure_header_written(self):
+        if not self._nframeswritten:
+            if not self._nchannels:
+                raise Error('# of channels not specified')
+            if not self._sampwidth:
+                raise Error('sample width not specified')
+            if not self._framerate:
+                raise Error('frame rate not specified')
+            self._write_header()
+
+    def _write_header(self):
+        if self._comptype == 'NONE':
+            if self._sampwidth == 1:
+                encoding = AUDIO_FILE_ENCODING_LINEAR_8
+                self._framesize = 1
+            elif self._sampwidth == 2:
+                encoding = AUDIO_FILE_ENCODING_LINEAR_16
+                self._framesize = 2
+            elif self._sampwidth == 3:
+                encoding = AUDIO_FILE_ENCODING_LINEAR_24
+                self._framesize = 3
+            elif self._sampwidth == 4:
+                encoding = AUDIO_FILE_ENCODING_LINEAR_32
+                self._framesize = 4
+            else:
+                raise Error('internal error')
+        elif self._comptype == 'ULAW':
+            encoding = AUDIO_FILE_ENCODING_MULAW_8
+            self._framesize = 1
+        else:
+            raise Error('internal error')
+        self._framesize = self._framesize * self._nchannels
+        _write_u32(self._file, AUDIO_FILE_MAGIC)
+        header_size = 25 + len(self._info)
+        header_size = (header_size + 7) & ~7
+        _write_u32(self._file, header_size)
+        if self._nframes == AUDIO_UNKNOWN_SIZE:
+            length = AUDIO_UNKNOWN_SIZE
+        else:
+            length = self._nframes * self._framesize
+        try:
+            self._form_length_pos = self._file.tell()
+        except (AttributeError, OSError):
+            self._form_length_pos = None
+        _write_u32(self._file, length)
+        self._datalength = length
+        _write_u32(self._file, encoding)
+        _write_u32(self._file, self._framerate)
+        _write_u32(self._file, self._nchannels)
+        self._file.write(self._info)
+        self._file.write(b'\0'*(header_size - len(self._info) - 24))
+
+    def _patchheader(self):
+        if self._form_length_pos is None:
+            raise OSError('cannot seek')
+        self._file.seek(self._form_length_pos)
+        _write_u32(self._file, self._datawritten)
+        self._datalength = self._datawritten
+        self._file.seek(0, 2)
+
+def open(f, mode=None):
+    if mode is None:
+        if hasattr(f, 'mode'):
+            mode = f.mode
+        else:
+            mode = 'rb'
+    if mode in ('r', 'rb'):
+        return Au_read(f)
+    elif mode in ('w', 'wb'):
+        return Au_write(f)
+    else:
+        raise Error("mode must be 'r', 'rb', 'w', or 'wb'")
+
+def openfp(f, mode=None):
+    warnings.warn("sunau.openfp is deprecated since Python 3.7. "
+                  "Use sunau.open instead.", DeprecationWarning, stacklevel=2)
+    return open(f, mode=mode)
diff --git a/Lib/unittest/__main__.py b/Lib/unittest/__main__.py
index 711653832..e5876f569 100644
--- a/Lib/unittest/__main__.py
+++ b/Lib/unittest/__main__.py
@@ -2,8 +2,7 @@
 
 import sys
 if sys.argv[0].endswith("__main__.py"):
-    # FIXME change to `import os.path` as it was for cpython once `import os.path` works
-    import os
+    import os.path
     # We change sys.argv[0] to make help message more useful
     # use executable without path, unquoted
     # (it's just a hint anyway)
diff --git a/README.md b/README.md
index 009135660..b28ba7133 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,10 @@ A Python-3 (CPython >= 3.5.0) Interpreter written in Rust :snake: :scream:
 
 #### Check out our [online demo](https://rustpython.github.io/demo/) running on WebAssembly.
 
+RustPython requires Rust 1.36 or higher. 
+To check Rust version: `rustc --version` If you wish to update,
+`rustup update stable`.
+
 To test RustPython, do the following:
 
     $ git clone https://github.com/RustPython/RustPython
diff --git a/benchmarks/bench.rs b/benchmarks/bench.rs
index 5a67ac392..60252ebe2 100644
--- a/benchmarks/bench.rs
+++ b/benchmarks/bench.rs
@@ -94,7 +94,7 @@ fn bench_rustpy_nbody(b: &mut test::Bencher) {
 
     let vm = VirtualMachine::default();
 
-    let code = match vm.compile(source, &compile::Mode::Single, "<stdin>".to_string()) {
+    let code = match vm.compile(source, compile::Mode::Single, "<stdin>".to_string()) {
         Ok(code) => code,
         Err(e) => panic!("{:?}", e),
     };
@@ -113,7 +113,7 @@ fn bench_rustpy_mandelbrot(b: &mut test::Bencher) {
 
     let vm = VirtualMachine::default();
 
-    let code = match vm.compile(source, &compile::Mode::Single, "<stdin>".to_string()) {
+    let code = match vm.compile(source, compile::Mode::Single, "<stdin>".to_string()) {
         Ok(code) => code,
         Err(e) => panic!("{:?}", e),
     };
diff --git a/benchmarks/test_benchmarks.py b/benchmarks/test_benchmarks.py
index 49c9a1ada..c1b80582d 100644
--- a/benchmarks/test_benchmarks.py
+++ b/benchmarks/test_benchmarks.py
@@ -1,4 +1,5 @@
 
+import os
 import time
 import sys
 
@@ -19,8 +20,11 @@ benchmarks = [
     ['benchmarks/mandelbrot.py'],
 ]
 
-@pytest.mark.parametrize('exe', pythons)
-@pytest.mark.parametrize('args', benchmarks)
+exe_ids = ['cpython', 'rustpython']
+benchmark_ids = [benchmark[0].split('/')[-1] for benchmark in benchmarks]
+
+@pytest.mark.parametrize('exe', pythons, ids=exe_ids)
+@pytest.mark.parametrize('args', benchmarks, ids=benchmark_ids)
 def test_bench(exe, args, benchmark):
     def bench():
         subprocess.run([exe] + args)
diff --git a/bytecode/src/bytecode.rs b/bytecode/src/bytecode.rs
index 0d5008b83..3802429b8 100644
--- a/bytecode/src/bytecode.rs
+++ b/bytecode/src/bytecode.rs
@@ -84,10 +84,7 @@ pub enum Instruction {
         symbols: Vec<String>,
         level: usize,
     },
-    ImportStar {
-        name: Option<String>,
-        level: usize,
-    },
+    ImportStar,
     ImportFrom {
         name: String,
     },
@@ -138,12 +135,24 @@ pub enum Instruction {
     Jump {
         target: Label,
     },
-    JumpIf {
+    /// Pop the top of the stack, and jump if this value is true.
+    JumpIfTrue {
         target: Label,
     },
+    /// Pop the top of the stack, and jump if this value is false.
     JumpIfFalse {
         target: Label,
     },
+    /// Peek at the top of the stack, and jump if this value is true.
+    /// Otherwise, pop top of stack.
+    JumpIfTrueOrPop {
+        target: Label,
+    },
+    /// Peek at the top of the stack, and jump if this value is false.
+    /// Otherwise, pop top of stack.
+    JumpIfFalseOrPop {
+        target: Label,
+    },
     MakeFunction {
         flags: FunctionOpArg,
     },
@@ -336,10 +345,13 @@ impl CodeObject {
             }
         })
     }
-}
 
-impl fmt::Display for CodeObject {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn display_inner(
+        &self,
+        f: &mut fmt::Formatter,
+        expand_codeobjects: bool,
+        level: usize,
+    ) -> fmt::Result {
         let label_targets: HashSet<&usize> = self.label_map.values().collect();
         for (offset, instruction) in self.instructions.iter().enumerate() {
             let arrow = if label_targets.contains(&offset) {
@@ -347,15 +359,40 @@ impl fmt::Display for CodeObject {
             } else {
                 "  "
             };
-            write!(f, "          {} {:5} ", arrow, offset)?;
-            instruction.fmt_dis(f, &self.label_map)?;
+            for _ in 0..level {
+                write!(f, "          ")?;
+            }
+            write!(f, "{} {:5} ", arrow, offset)?;
+            instruction.fmt_dis(f, &self.label_map, expand_codeobjects, level)?;
         }
         Ok(())
     }
+
+    pub fn display_expand_codeobjects<'a>(&'a self) -> impl fmt::Display + 'a {
+        struct Display<'a>(&'a CodeObject);
+        impl fmt::Display for Display<'_> {
+            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                self.0.display_inner(f, true, 1)
+            }
+        }
+        Display(self)
+    }
+}
+
+impl fmt::Display for CodeObject {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.display_inner(f, false, 1)
+    }
 }
 
 impl Instruction {
-    fn fmt_dis(&self, f: &mut fmt::Formatter, label_map: &HashMap<Label, usize>) -> fmt::Result {
+    fn fmt_dis(
+        &self,
+        f: &mut fmt::Formatter,
+        label_map: &HashMap<Label, usize>,
+        expand_codeobjects: bool,
+        level: usize,
+    ) -> fmt::Result {
         macro_rules! w {
             ($variant:ident) => {
                 write!(f, "{:20}\n", stringify!($variant))
@@ -389,7 +426,7 @@ impl Instruction {
                 format!("{:?}", symbols),
                 level
             ),
-            ImportStar { name, level } => w!(ImportStar, format!("{:?}", name), level),
+            ImportStar => w!(ImportStar),
             ImportFrom { name } => w!(ImportFrom, name),
             LoadName { name, scope } => w!(LoadName, name, format!("{:?}", scope)),
             StoreName { name, scope } => w!(StoreName, name, format!("{:?}", scope)),
@@ -398,7 +435,14 @@ impl Instruction {
             DeleteSubscript => w!(DeleteSubscript),
             StoreAttr { name } => w!(StoreAttr, name),
             DeleteAttr { name } => w!(DeleteAttr, name),
-            LoadConst { value } => w!(LoadConst, value),
+            LoadConst { value } => match value {
+                Constant::Code { code } if expand_codeobjects => {
+                    writeln!(f, "LoadConst ({:?}):", code)?;
+                    code.display_inner(f, true, level + 1)?;
+                    Ok(())
+                }
+                _ => w!(LoadConst, value),
+            },
             UnaryOperation { op } => w!(UnaryOperation, format!("{:?}", op)),
             BinaryOperation { op, inplace } => w!(BinaryOperation, format!("{:?}", op), inplace),
             LoadAttr { name } => w!(LoadAttr, name),
@@ -411,8 +455,10 @@ impl Instruction {
             Continue => w!(Continue),
             Break => w!(Break),
             Jump { target } => w!(Jump, label_map[target]),
-            JumpIf { target } => w!(JumpIf, label_map[target]),
+            JumpIfTrue { target } => w!(JumpIfTrue, label_map[target]),
             JumpIfFalse { target } => w!(JumpIfFalse, label_map[target]),
+            JumpIfTrueOrPop { target } => w!(JumpIfTrueOrPop, label_map[target]),
+            JumpIfFalseOrPop { target } => w!(JumpIfFalseOrPop, label_map[target]),
             MakeFunction { flags } => w!(MakeFunction, format!("{:?}", flags)),
             CallFunction { typ } => w!(CallFunction, format!("{:?}", typ)),
             ForIter { target } => w!(ForIter, label_map[target]),
diff --git a/compiler/src/compile.rs b/compiler/src/compile.rs
index a13d3617e..23b46f1b9 100644
--- a/compiler/src/compile.rs
+++ b/compiler/src/compile.rs
@@ -8,16 +8,19 @@
 use crate::error::{CompileError, CompileErrorType};
 use crate::output_stream::{CodeObjectStream, OutputStream};
 use crate::peephole::PeepholeOptimizer;
-use crate::symboltable::{make_symbol_table, statements_to_symbol_table, Symbol, SymbolScope};
+use crate::symboltable::{
+    make_symbol_table, statements_to_symbol_table, Symbol, SymbolScope, SymbolTable,
+};
 use num_complex::Complex64;
 use rustpython_bytecode::bytecode::{self, CallType, CodeObject, Instruction, Varargs};
 use rustpython_parser::{ast, parser};
 
 type BasicOutputStream = PeepholeOptimizer<CodeObjectStream>;
 
+/// Main structure holding the state of compilation.
 struct Compiler<O: OutputStream = BasicOutputStream> {
     output_stack: Vec<O>,
-    scope_stack: Vec<SymbolScope>,
+    symbol_table_stack: Vec<SymbolTable>,
     nxt_label: usize,
     source_path: Option<String>,
     current_source_location: ast::Location,
@@ -30,7 +33,7 @@ struct Compiler<O: OutputStream = BasicOutputStream> {
 /// Compile a given sourcecode into a bytecode object.
 pub fn compile(
     source: &str,
-    mode: &Mode,
+    mode: Mode,
     source_path: String,
     optimize: u8,
 ) -> Result<CodeObject, CompileError> {
@@ -101,16 +104,34 @@ pub fn compile_program_single(
     })
 }
 
+#[derive(Clone, Copy)]
 pub enum Mode {
     Exec,
     Eval,
     Single,
 }
 
-#[derive(Clone, Copy)]
-enum EvalContext {
-    Statement,
-    Expression,
+impl std::str::FromStr for Mode {
+    type Err = ModeParseError;
+    fn from_str(s: &str) -> Result<Self, ModeParseError> {
+        match s {
+            "exec" => Ok(Mode::Exec),
+            "eval" => Ok(Mode::Eval),
+            "single" => Ok(Mode::Single),
+            _ => Err(ModeParseError { _priv: () }),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct ModeParseError {
+    _priv: (),
+}
+
+impl std::fmt::Display for ModeParseError {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        write!(f, r#"mode should be "exec", "eval", or "single""#)
+    }
 }
 
 pub(crate) type Label = usize;
@@ -128,7 +149,7 @@ impl<O: OutputStream> Compiler<O> {
     fn new(optimize: u8) -> Self {
         Compiler {
             output_stack: Vec::new(),
-            scope_stack: Vec::new(),
+            symbol_table_stack: Vec::new(),
             nxt_label: 0,
             source_path: None,
             current_source_location: ast::Location::default(),
@@ -163,11 +184,23 @@ impl<O: OutputStream> Compiler<O> {
     fn compile_program(
         &mut self,
         program: &ast::Program,
-        symbol_scope: SymbolScope,
+        symbol_table: SymbolTable,
     ) -> Result<(), CompileError> {
         let size_before = self.output_stack.len();
-        self.scope_stack.push(symbol_scope);
-        self.compile_statements(&program.statements)?;
+        self.symbol_table_stack.push(symbol_table);
+
+        let (statements, doc) = get_doc(&program.statements);
+        if let Some(value) = doc {
+            self.emit(Instruction::LoadConst {
+                value: bytecode::Constant::String { value },
+            });
+            self.emit(Instruction::StoreName {
+                name: "__doc__".to_owned(),
+                scope: bytecode::NameScope::Global,
+            });
+        }
+        self.compile_statements(statements)?;
+
         assert_eq!(self.output_stack.len(), size_before);
 
         // Emit None at end:
@@ -181,9 +214,9 @@ impl<O: OutputStream> Compiler<O> {
     fn compile_program_single(
         &mut self,
         program: &ast::Program,
-        symbol_scope: SymbolScope,
+        symbol_table: SymbolTable,
     ) -> Result<(), CompileError> {
-        self.scope_stack.push(symbol_scope);
+        self.symbol_table_stack.push(symbol_table);
 
         let mut emitted_return = false;
 
@@ -220,9 +253,9 @@ impl<O: OutputStream> Compiler<O> {
     fn compile_statement_eval(
         &mut self,
         statements: &[ast::Statement],
-        symbol_table: SymbolScope,
+        symbol_table: SymbolTable,
     ) -> Result<(), CompileError> {
-        self.scope_stack.push(symbol_table);
+        self.symbol_table_stack.push(symbol_table);
         for statement in statements {
             if let ast::StatementType::Expression { ref expression } = statement.node {
                 self.compile_expression(expression)?;
@@ -246,12 +279,11 @@ impl<O: OutputStream> Compiler<O> {
 
     fn scope_for_name(&self, name: &str) -> bytecode::NameScope {
         let symbol = self.lookup_name(name);
-        if symbol.is_global {
-            bytecode::NameScope::Global
-        } else if symbol.is_nonlocal {
-            bytecode::NameScope::NonLocal
-        } else {
-            bytecode::NameScope::Local
+        match symbol.scope {
+            SymbolScope::Global => bytecode::NameScope::Global,
+            SymbolScope::Nonlocal => bytecode::NameScope::NonLocal,
+            SymbolScope::Unknown => bytecode::NameScope::Local,
+            SymbolScope::Local => bytecode::NameScope::Local,
         }
     }
 
@@ -285,11 +317,15 @@ impl<O: OutputStream> Compiler<O> {
                         symbols: vec![],
                         level: 0,
                     });
-
                     if let Some(alias) = &name.alias {
+                        for part in name.symbol.split('.').skip(1) {
+                            self.emit(Instruction::LoadAttr {
+                                name: part.to_owned(),
+                            });
+                        }
                         self.store_name(alias);
                     } else {
-                        self.store_name(&name.symbol);
+                        self.store_name(name.symbol.split('.').next().unwrap());
                     }
                 }
             }
@@ -302,10 +338,12 @@ impl<O: OutputStream> Compiler<O> {
 
                 if import_star {
                     // from .... import *
-                    self.emit(Instruction::ImportStar {
+                    self.emit(Instruction::Import {
                         name: module.clone(),
+                        symbols: vec!["*".to_owned()],
                         level: *level,
                     });
+                    self.emit(Instruction::ImportStar);
                 } else {
                     // from mod import a, b as c
                     // First, determine the fromlist (for import lib):
@@ -350,14 +388,14 @@ impl<O: OutputStream> Compiler<O> {
                 match orelse {
                     None => {
                         // Only if:
-                        self.compile_test(test, None, Some(end_label), EvalContext::Statement)?;
+                        self.compile_jump_if(test, false, end_label)?;
                         self.compile_statements(body)?;
                         self.set_label(end_label);
                     }
                     Some(statements) => {
                         // if - else:
                         let else_label = self.new_label();
-                        self.compile_test(test, None, Some(else_label), EvalContext::Statement)?;
+                        self.compile_jump_if(test, false, else_label)?;
                         self.compile_statements(body)?;
                         self.emit(Instruction::Jump { target: end_label });
 
@@ -459,7 +497,7 @@ impl<O: OutputStream> Compiler<O> {
                 // if some flag, ignore all assert statements!
                 if self.optimize == 0 {
                     let end_label = self.new_label();
-                    self.compile_test(test, Some(end_label), None, EvalContext::Statement)?;
+                    self.compile_jump_if(test, true, end_label)?;
                     self.emit(Instruction::LoadName {
                         name: String::from("AssertionError"),
                         scope: bytecode::NameScope::Local,
@@ -1006,7 +1044,7 @@ impl<O: OutputStream> Compiler<O> {
 
         self.set_label(start_label);
 
-        self.compile_test(test, None, Some(else_label), EvalContext::Statement)?;
+        self.compile_jump_if(test, false, else_label)?;
 
         let was_in_loop = self.in_loop;
         self.in_loop = true;
@@ -1118,12 +1156,9 @@ impl<O: OutputStream> Compiler<O> {
             });
 
             // if comparison result is false, we break with this value; if true, try the next one.
-            // (CPython compresses these three opcodes into JUMP_IF_FALSE_OR_POP)
-            self.emit(Instruction::Duplicate);
-            self.emit(Instruction::JumpIfFalse {
+            self.emit(Instruction::JumpIfFalseOrPop {
                 target: break_label,
             });
-            self.emit(Instruction::Pop);
         }
 
         // handle the last comparison
@@ -1256,66 +1291,120 @@ impl<O: OutputStream> Compiler<O> {
         self.emit(Instruction::BinaryOperation { op: i, inplace });
     }
 
-    fn compile_test(
+    /// Implement boolean short circuit evaluation logic.
+    /// https://en.wikipedia.org/wiki/Short-circuit_evaluation
+    ///
+    /// This means, in a boolean statement 'x and y' the variable y will
+    /// not be evaluated when x is false.
+    ///
+    /// The idea is to jump to a label if the expression is either true or false
+    /// (indicated by the condition parameter).
+    fn compile_jump_if(
         &mut self,
         expression: &ast::Expression,
-        true_label: Option<Label>,
-        false_label: Option<Label>,
-        context: EvalContext,
+        condition: bool,
+        target_label: Label,
     ) -> Result<(), CompileError> {
         // Compile expression for test, and jump to label if false
         match &expression.node {
-            ast::ExpressionType::BoolOp { a, op, b } => match op {
-                ast::BooleanOperator::And => {
-                    let f = false_label.unwrap_or_else(|| self.new_label());
-                    self.compile_test(a, None, Some(f), context)?;
-                    self.compile_test(b, true_label, false_label, context)?;
-                    if false_label.is_none() {
-                        self.set_label(f);
-                    }
-                }
-                ast::BooleanOperator::Or => {
-                    let t = true_label.unwrap_or_else(|| self.new_label());
-                    self.compile_test(a, Some(t), None, context)?;
-                    self.compile_test(b, true_label, false_label, context)?;
-                    if true_label.is_none() {
-                        self.set_label(t);
-                    }
-                }
-            },
-            _ => {
-                self.compile_expression(expression)?;
-                match context {
-                    EvalContext::Statement => {
-                        if let Some(true_label) = true_label {
-                            self.emit(Instruction::JumpIf { target: true_label });
-                        }
-                        if let Some(false_label) = false_label {
-                            self.emit(Instruction::JumpIfFalse {
-                                target: false_label,
-                            });
+            ast::ExpressionType::BoolOp { op, values } => {
+                match op {
+                    ast::BooleanOperator::And => {
+                        if condition {
+                            // If all values are true.
+                            let end_label = self.new_label();
+                            let (last_value, values) = values.split_last().unwrap();
+
+                            // If any of the values is false, we can short-circuit.
+                            for value in values {
+                                self.compile_jump_if(value, false, end_label)?;
+                            }
+
+                            // It depends upon the last value now: will it be true?
+                            self.compile_jump_if(last_value, true, target_label)?;
+                            self.set_label(end_label);
+                        } else {
+                            // If any value is false, the whole condition is false.
+                            for value in values {
+                                self.compile_jump_if(value, false, target_label)?;
+                            }
                         }
                     }
-                    EvalContext::Expression => {
-                        if let Some(true_label) = true_label {
-                            self.emit(Instruction::Duplicate);
-                            self.emit(Instruction::JumpIf { target: true_label });
-                            self.emit(Instruction::Pop);
-                        }
-                        if let Some(false_label) = false_label {
-                            self.emit(Instruction::Duplicate);
-                            self.emit(Instruction::JumpIfFalse {
-                                target: false_label,
-                            });
-                            self.emit(Instruction::Pop);
+                    ast::BooleanOperator::Or => {
+                        if condition {
+                            // If any of the values is true.
+                            for value in values {
+                                self.compile_jump_if(value, true, target_label)?;
+                            }
+                        } else {
+                            // If all of the values are false.
+                            let end_label = self.new_label();
+                            let (last_value, values) = values.split_last().unwrap();
+
+                            // If any value is true, we can short-circuit:
+                            for value in values {
+                                self.compile_jump_if(value, true, end_label)?;
+                            }
+
+                            // It all depends upon the last value now!
+                            self.compile_jump_if(last_value, false, target_label)?;
+                            self.set_label(end_label);
                         }
                     }
                 }
             }
+            ast::ExpressionType::Unop {
+                op: ast::UnaryOperator::Not,
+                a,
+            } => {
+                self.compile_jump_if(a, !condition, target_label)?;
+            }
+            _ => {
+                // Fall back case which always will work!
+                self.compile_expression(expression)?;
+                if condition {
+                    self.emit(Instruction::JumpIfTrue {
+                        target: target_label,
+                    });
+                } else {
+                    self.emit(Instruction::JumpIfFalse {
+                        target: target_label,
+                    });
+                }
+            }
         }
         Ok(())
     }
 
+    /// Compile a boolean operation as an expression.
+    /// This means, that the last value remains on the stack.
+    fn compile_bool_op(
+        &mut self,
+        op: &ast::BooleanOperator,
+        values: &[ast::Expression],
+    ) -> Result<(), CompileError> {
+        let end_label = self.new_label();
+
+        let (last_value, values) = values.split_last().unwrap();
+        for value in values {
+            self.compile_expression(value)?;
+
+            match op {
+                ast::BooleanOperator::And => {
+                    self.emit(Instruction::JumpIfFalseOrPop { target: end_label });
+                }
+                ast::BooleanOperator::Or => {
+                    self.emit(Instruction::JumpIfTrueOrPop { target: end_label });
+                }
+            }
+        }
+
+        // If all values did not qualify, take the value of the last value:
+        self.compile_expression(last_value)?;
+        self.set_label(end_label);
+        Ok(())
+    }
+
     fn compile_expression(&mut self, expression: &ast::Expression) -> Result<(), CompileError> {
         trace!("Compiling {:?}", expression);
         self.set_source_location(&expression.location);
@@ -1327,12 +1416,7 @@ impl<O: OutputStream> Compiler<O> {
                 args,
                 keywords,
             } => self.compile_call(function, args, keywords)?,
-            BoolOp { .. } => self.compile_test(
-                expression,
-                Option::None,
-                Option::None,
-                EvalContext::Expression,
-            )?,
+            BoolOp { op, values } => self.compile_bool_op(op, values)?,
             Binop { a, op, b } => {
                 self.compile_expression(a)?;
                 self.compile_expression(b)?;
@@ -1527,8 +1611,7 @@ impl<O: OutputStream> Compiler<O> {
             IfExpression { test, body, orelse } => {
                 let no_label = self.new_label();
                 let end_label = self.new_label();
-                self.compile_test(test, Option::None, Option::None, EvalContext::Expression)?;
-                self.emit(Instruction::JumpIfFalse { target: no_label });
+                self.compile_jump_if(test, false, no_label)?;
                 // True case
                 self.compile_expression(body)?;
                 self.emit(Instruction::Jump { target: end_label });
@@ -1745,12 +1828,7 @@ impl<O: OutputStream> Compiler<O> {
 
             // Now evaluate the ifs:
             for if_condition in &generator.ifs {
-                self.compile_test(
-                    if_condition,
-                    None,
-                    Some(start_label),
-                    EvalContext::Statement,
-                )?
+                self.compile_jump_if(if_condition, false, start_label)?
             }
         }
 
@@ -1831,30 +1909,36 @@ impl<O: OutputStream> Compiler<O> {
     }
 
     fn compile_string(&mut self, string: &ast::StringGroup) -> Result<(), CompileError> {
-        match string {
-            ast::StringGroup::Joined { values } => {
-                for value in values {
-                    self.compile_string(value)?;
+        if let Some(value) = try_get_constant_string(string) {
+            self.emit(Instruction::LoadConst {
+                value: bytecode::Constant::String { value },
+            });
+        } else {
+            match string {
+                ast::StringGroup::Joined { values } => {
+                    for value in values {
+                        self.compile_string(value)?;
+                    }
+                    self.emit(Instruction::BuildString { size: values.len() })
+                }
+                ast::StringGroup::Constant { value } => {
+                    self.emit(Instruction::LoadConst {
+                        value: bytecode::Constant::String {
+                            value: value.to_string(),
+                        },
+                    });
+                }
+                ast::StringGroup::FormattedValue {
+                    value,
+                    conversion,
+                    spec,
+                } => {
+                    self.compile_expression(value)?;
+                    self.emit(Instruction::FormatValue {
+                        conversion: conversion.map(compile_conversion_flag),
+                        spec: spec.clone(),
+                    });
                 }
-                self.emit(Instruction::BuildString { size: values.len() })
-            }
-            ast::StringGroup::Constant { value } => {
-                self.emit(Instruction::LoadConst {
-                    value: bytecode::Constant::String {
-                        value: value.to_string(),
-                    },
-                });
-            }
-            ast::StringGroup::FormattedValue {
-                value,
-                conversion,
-                spec,
-            } => {
-                self.compile_expression(value)?;
-                self.emit(Instruction::FormatValue {
-                    conversion: conversion.map(compile_conversion_flag),
-                    spec: spec.clone(),
-                });
             }
         }
         Ok(())
@@ -1862,22 +1946,29 @@ impl<O: OutputStream> Compiler<O> {
 
     // Scope helpers:
     fn enter_scope(&mut self) {
-        // println!("Enter scope {:?}", self.scope_stack);
+        // println!("Enter scope {:?}", self.symbol_table_stack);
         // Enter first subscope!
-        let scope = self.scope_stack.last_mut().unwrap().sub_scopes.remove(0);
-        self.scope_stack.push(scope);
+        let table = self
+            .symbol_table_stack
+            .last_mut()
+            .unwrap()
+            .sub_tables
+            .remove(0);
+        self.symbol_table_stack.push(table);
     }
 
     fn leave_scope(&mut self) {
-        // println!("Leave scope {:?}", self.scope_stack);
-        let scope = self.scope_stack.pop().unwrap();
-        assert!(scope.sub_scopes.is_empty());
+        // println!("Leave scope {:?}", self.symbol_table_stack);
+        let table = self.symbol_table_stack.pop().unwrap();
+        assert!(table.sub_tables.is_empty());
     }
 
     fn lookup_name(&self, name: &str) -> &Symbol {
         // println!("Looking up {:?}", name);
-        let scope = self.scope_stack.last().unwrap();
-        scope.lookup(name).unwrap()
+        let symbol_table = self.symbol_table_stack.last().unwrap();
+        symbol_table.lookup(name).expect(
+            "The symbol must be present in the symbol table, even when it is undefined in python.",
+        )
     }
 
     // Low level helper functions:
@@ -1927,13 +2018,11 @@ impl<O: OutputStream> Compiler<O> {
 }
 
 fn get_doc(body: &[ast::Statement]) -> (&[ast::Statement], Option<String>) {
-    if let Some(val) = body.get(0) {
+    if let Some((val, body_rest)) = body.split_first() {
         if let ast::StatementType::Expression { ref expression } = val.node {
             if let ast::ExpressionType::String { value } = &expression.node {
-                if let ast::StringGroup::Constant { ref value } = value {
-                    if let Some((_, body_rest)) = body.split_first() {
-                        return (body_rest, Some(value.to_string()));
-                    }
+                if let Some(value) = try_get_constant_string(value) {
+                    return (body_rest, Some(value.to_string()));
                 }
             }
         }
@@ -1941,6 +2030,27 @@ fn get_doc(body: &[ast::Statement]) -> (&[ast::Statement], Option<String>) {
     (body, None)
 }
 
+fn try_get_constant_string(string: &ast::StringGroup) -> Option<String> {
+    fn get_constant_string_inner(out_string: &mut String, string: &ast::StringGroup) -> bool {
+        match string {
+            ast::StringGroup::Constant { value } => {
+                out_string.push_str(&value);
+                true
+            }
+            ast::StringGroup::Joined { values } => values
+                .iter()
+                .all(|value| get_constant_string_inner(out_string, value)),
+            ast::StringGroup::FormattedValue { .. } => false,
+        }
+    }
+    let mut out_string = String::new();
+    if get_constant_string_inner(&mut out_string, string) {
+        Some(out_string)
+    } else {
+        None
+    }
+}
+
 fn compile_location(location: &ast::Location) -> bytecode::Location {
     bytecode::Location::new(location.row(), location.column())
 }
@@ -1988,11 +2098,11 @@ mod tests {
                 LoadConst {
                     value: Boolean { value: true }
                 },
-                JumpIf { target: 1 },
+                JumpIfTrue { target: 1 },
                 LoadConst {
                     value: Boolean { value: false }
                 },
-                JumpIf { target: 1 },
+                JumpIfTrue { target: 1 },
                 LoadConst {
                     value: Boolean { value: false }
                 },
@@ -2042,7 +2152,7 @@ mod tests {
                 LoadConst {
                     value: Boolean { value: false }
                 },
-                JumpIf { target: 1 },
+                JumpIfTrue { target: 1 },
                 LoadConst {
                     value: Boolean { value: false }
                 },
diff --git a/compiler/src/symboltable.rs b/compiler/src/symboltable.rs
index c1db24bf3..8e44bc755 100644
--- a/compiler/src/symboltable.rs
+++ b/compiler/src/symboltable.rs
@@ -12,47 +12,59 @@ use indexmap::map::IndexMap;
 use rustpython_parser::ast;
 use rustpython_parser::location::Location;
 
-pub fn make_symbol_table(program: &ast::Program) -> Result<SymbolScope, SymbolTableError> {
+pub fn make_symbol_table(program: &ast::Program) -> Result<SymbolTable, SymbolTableError> {
     let mut builder: SymbolTableBuilder = Default::default();
-    builder.enter_scope();
+    builder.prepare();
     builder.scan_program(program)?;
-    assert_eq!(builder.scopes.len(), 1);
-
-    let symbol_table = builder.scopes.pop().unwrap();
-    analyze_symbol_table(&symbol_table, None)?;
-    Ok(symbol_table)
+    builder.finish()
 }
 
 pub fn statements_to_symbol_table(
     statements: &[ast::Statement],
-) -> Result<SymbolScope, SymbolTableError> {
+) -> Result<SymbolTable, SymbolTableError> {
     let mut builder: SymbolTableBuilder = Default::default();
-    builder.enter_scope();
+    builder.prepare();
     builder.scan_statements(statements)?;
-    assert_eq!(builder.scopes.len(), 1);
-
-    let symbol_table = builder.scopes.pop().unwrap();
-    analyze_symbol_table(&symbol_table, None)?;
-    Ok(symbol_table)
+    builder.finish()
 }
 
 /// Captures all symbols in the current scope, and has a list of subscopes in this scope.
 #[derive(Clone, Default)]
-pub struct SymbolScope {
+pub struct SymbolTable {
     /// A set of symbols present on this scope level.
     pub symbols: IndexMap<String, Symbol>,
 
     /// A list of subscopes in the order as found in the
     /// AST nodes.
-    pub sub_scopes: Vec<SymbolScope>,
+    pub sub_tables: Vec<SymbolTable>,
 }
 
+impl SymbolTable {
+    fn new() -> Self {
+        SymbolTable {
+            symbols: Default::default(),
+            sub_tables: vec![],
+        }
+    }
+}
+
+/// Indicator for a single symbol what the scope of this symbol is.
+/// The scope can be unknown, which is unfortunate, but not impossible.
+#[derive(Debug, Clone)]
+pub enum SymbolScope {
+    Global,
+    Nonlocal,
+    Local,
+    Unknown,
+}
+
+/// A single symbol in a table. Has various properties such as the scope
+/// of the symbol, and also the various uses of the symbol.
 #[derive(Debug, Clone)]
 pub struct Symbol {
     pub name: String,
-    pub is_global: bool,
-    pub is_local: bool,
-    pub is_nonlocal: bool,
+    // pub table: SymbolTableRef,
+    pub scope: SymbolScope,
     pub is_param: bool,
     pub is_referenced: bool,
     pub is_assigned: bool,
@@ -64,9 +76,8 @@ impl Symbol {
     fn new(name: &str) -> Self {
         Symbol {
             name: name.to_string(),
-            is_global: false,
-            is_local: false,
-            is_nonlocal: false,
+            // table,
+            scope: SymbolScope::Unknown,
             is_param: false,
             is_referenced: false,
             is_assigned: false,
@@ -74,6 +85,22 @@ impl Symbol {
             is_free: false,
         }
     }
+
+    pub fn is_global(&self) -> bool {
+        if let SymbolScope::Global = self.scope {
+            true
+        } else {
+            false
+        }
+    }
+
+    pub fn is_local(&self) -> bool {
+        if let SymbolScope::Local = self.scope {
+            true
+        } else {
+            false
+        }
+    }
 }
 
 #[derive(Debug)]
@@ -93,19 +120,19 @@ impl From<SymbolTableError> for CompileError {
 
 type SymbolTableResult = Result<(), SymbolTableError>;
 
-impl SymbolScope {
+impl SymbolTable {
     pub fn lookup(&self, name: &str) -> Option<&Symbol> {
         self.symbols.get(name)
     }
 }
 
-impl std::fmt::Debug for SymbolScope {
+impl std::fmt::Debug for SymbolTable {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         write!(
             f,
-            "SymbolScope({:?} symbols, {:?} sub scopes)",
+            "SymbolTable({:?} symbols, {:?} sub scopes)",
             self.symbols.len(),
-            self.sub_scopes.len()
+            self.sub_tables.len()
         )
     }
 }
@@ -113,75 +140,127 @@ impl std::fmt::Debug for SymbolScope {
 /* Perform some sort of analysis on nonlocals, globals etc..
   See also: https://github.com/python/cpython/blob/master/Python/symtable.c#L410
 */
-fn analyze_symbol_table(
-    symbol_scope: &SymbolScope,
-    parent_symbol_scope: Option<&SymbolScope>,
-) -> SymbolTableResult {
-    // Analyze sub scopes:
-    for sub_scope in &symbol_scope.sub_scopes {
-        analyze_symbol_table(&sub_scope, Some(symbol_scope))?;
-    }
-
-    // Analyze symbols:
-    for symbol in symbol_scope.symbols.values() {
-        analyze_symbol(symbol, parent_symbol_scope)?;
-    }
-
-    Ok(())
+fn analyze_symbol_table(symbol_table: &mut SymbolTable) -> SymbolTableResult {
+    let mut analyzer = SymbolTableAnalyzer::default();
+    analyzer.analyze_symbol_table(symbol_table)
 }
 
-fn analyze_symbol(symbol: &Symbol, parent_symbol_scope: Option<&SymbolScope>) -> SymbolTableResult {
-    if symbol.is_nonlocal {
-        // check if name is defined in parent scope!
-        if let Some(parent_symbol_scope) = parent_symbol_scope {
-            if !parent_symbol_scope.symbols.contains_key(&symbol.name) {
-                return Err(SymbolTableError {
-                    error: format!("no binding for nonlocal '{}' found", symbol.name),
-                    location: Default::default(),
-                });
-            }
-        } else {
-            return Err(SymbolTableError {
-                error: format!(
-                    "nonlocal {} defined at place without an enclosing scope",
-                    symbol.name
-                ),
-                location: Default::default(),
-            });
+/// Symbol table analysis. Can be used to analyze a fully
+/// build symbol table structure. It will mark variables
+/// as local variables for example.
+#[derive(Default)]
+struct SymbolTableAnalyzer {
+    tables: Vec<SymbolTable>,
+}
+
+impl SymbolTableAnalyzer {
+    fn analyze_symbol_table(&mut self, symbol_table: &mut SymbolTable) -> SymbolTableResult {
+        // Store a copy to determine the parent.
+        // TODO: this should be improved to resolve this clone action.
+        self.tables.push(symbol_table.clone());
+
+        // Analyze sub scopes:
+        for sub_table in &mut symbol_table.sub_tables {
+            self.analyze_symbol_table(sub_table)?;
         }
+        self.tables.pop();
+
+        // Analyze symbols:
+        for symbol in symbol_table.symbols.values_mut() {
+            self.analyze_symbol(symbol)?;
+        }
+
+        Ok(())
     }
 
-    // TODO: add more checks for globals
+    fn analyze_symbol(&self, symbol: &mut Symbol) -> SymbolTableResult {
+        match symbol.scope {
+            SymbolScope::Nonlocal => {
+                // check if name is defined in parent table!
+                let parent_symbol_table: Option<&SymbolTable> = self.tables.last();
+                // symbol.table.borrow().parent.clone();
 
-    Ok(())
+                if let Some(table) = parent_symbol_table {
+                    if !table.symbols.contains_key(&symbol.name) {
+                        return Err(SymbolTableError {
+                            error: format!("no binding for nonlocal '{}' found", symbol.name),
+                            location: Default::default(),
+                        });
+                    }
+                } else {
+                    return Err(SymbolTableError {
+                        error: format!(
+                            "nonlocal {} defined at place without an enclosing scope",
+                            symbol.name
+                        ),
+                        location: Default::default(),
+                    });
+                }
+            }
+            SymbolScope::Global => {
+                // TODO: add more checks for globals?
+            }
+            SymbolScope::Local => {
+                // all is well
+            }
+            SymbolScope::Unknown => {
+                if symbol.is_assigned {
+                    symbol.scope = SymbolScope::Local;
+                }
+            }
+        }
+        Ok(())
+    }
 }
 
 #[derive(Debug, Clone)]
-enum SymbolRole {
+enum SymbolUsage {
     Global,
     Nonlocal,
     Used,
     Assigned,
+    Parameter,
 }
 
 #[derive(Default)]
 struct SymbolTableBuilder {
     // Scope stack.
-    scopes: Vec<SymbolScope>,
+    tables: Vec<SymbolTable>,
+}
+
+/// Enum to indicate in what mode an expression
+/// was used.
+/// In cpython this is stored in the AST, but I think this
+/// is not logical, since it is not context free.
+enum ExpressionContext {
+    Load,
+    Store,
+    Delete,
 }
 
 impl SymbolTableBuilder {
-    fn enter_scope(&mut self) {
-        let scope = Default::default();
-        self.scopes.push(scope);
-        // self.work_scopes.push(Default::default());
+    fn prepare(&mut self) {
+        let table = SymbolTable::new();
+        self.tables.push(table);
     }
 
-    fn leave_scope(&mut self) {
-        // Pop scope and add to subscopes of parent scope.
-        // let work_scope = self.work_scopes.pop().unwrap();
-        let scope = self.scopes.pop().unwrap();
-        self.scopes.last_mut().unwrap().sub_scopes.push(scope);
+    fn finish(&mut self) -> Result<SymbolTable, SymbolTableError> {
+        assert_eq!(self.tables.len(), 1);
+        let mut symbol_table = self.tables.pop().unwrap();
+        analyze_symbol_table(&mut symbol_table)?;
+        Ok(symbol_table)
+    }
+
+    fn enter_block(&mut self) {
+        // let parent = Some(self.tables.last().unwrap().clone());
+        let table = SymbolTable::new();
+        self.tables.push(table);
+    }
+
+    fn leave_block(&mut self) {
+        // Pop symbol table and add to sub table of parent table.
+        let table = self.tables.pop().unwrap();
+        self.tables.last_mut().unwrap().sub_tables.push(table);
     }
 
     fn scan_program(&mut self, program: &ast::Program) -> SymbolTableResult {
@@ -204,7 +283,7 @@ impl SymbolTableBuilder {
     }
 
     fn scan_parameter(&mut self, parameter: &ast::Parameter) -> SymbolTableResult {
-        self.register_name(&parameter.arg, SymbolRole::Assigned)
+        self.register_name(&parameter.arg, SymbolUsage::Parameter)
     }
 
     fn scan_parameters_annotations(&mut self, parameters: &[ast::Parameter]) -> SymbolTableResult {
@@ -216,7 +295,7 @@ impl SymbolTableBuilder {
 
     fn scan_parameter_annotation(&mut self, parameter: &ast::Parameter) -> SymbolTableResult {
         if let Some(annotation) = &parameter.annotation {
-            self.scan_expression(&annotation)?;
+            self.scan_expression(&annotation, &ExpressionContext::Load)?;
         }
         Ok(())
     }
@@ -226,12 +305,12 @@ impl SymbolTableBuilder {
         match &statement.node {
             Global { names } => {
                 for name in names {
-                    self.register_name(name, SymbolRole::Global)?;
+                    self.register_name(name, SymbolUsage::Global)?;
                 }
             }
             Nonlocal { names } => {
                 for name in names {
-                    self.register_name(name, SymbolRole::Nonlocal)?;
+                    self.register_name(name, SymbolUsage::Nonlocal)?;
                 }
             }
             FunctionDef {
@@ -242,16 +321,14 @@ impl SymbolTableBuilder {
                 returns,
                 ..
             } => {
-                self.scan_expressions(decorator_list)?;
-                self.register_name(name, SymbolRole::Assigned)?;
-
-                self.enter_function(args)?;
-
-                self.scan_statements(body)?;
+                self.scan_expressions(decorator_list, &ExpressionContext::Load)?;
+                self.register_name(name, SymbolUsage::Assigned)?;
                 if let Some(expression) = returns {
-                    self.scan_expression(expression)?;
+                    self.scan_expression(expression, &ExpressionContext::Load)?;
                 }
-                self.leave_scope();
+                self.enter_function(args)?;
+                self.scan_statements(body)?;
+                self.leave_block();
             }
             ClassDef {
                 name,
@@ -260,19 +337,21 @@ impl SymbolTableBuilder {
                 keywords,
                 decorator_list,
             } => {
-                self.register_name(name, SymbolRole::Assigned)?;
-                self.enter_scope();
+                self.register_name(name, SymbolUsage::Assigned)?;
+                self.enter_block();
                 self.scan_statements(body)?;
-                self.leave_scope();
-                self.scan_expressions(bases)?;
+                self.leave_block();
+                self.scan_expressions(bases, &ExpressionContext::Load)?;
                 for keyword in keywords {
-                    self.scan_expression(&keyword.value)?;
+                    self.scan_expression(&keyword.value, &ExpressionContext::Load)?;
                 }
-                self.scan_expressions(decorator_list)?;
+                self.scan_expressions(decorator_list, &ExpressionContext::Load)?;
+            }
+            Expression { expression } => {
+                self.scan_expression(expression, &ExpressionContext::Load)?
             }
-            Expression { expression } => self.scan_expression(expression)?,
             If { test, body, orelse } => {
-                self.scan_expression(test)?;
+                self.scan_expression(test, &ExpressionContext::Load)?;
                 self.scan_statements(body)?;
                 if let Some(code) = orelse {
                     self.scan_statements(code)?;
@@ -285,15 +364,15 @@ impl SymbolTableBuilder {
                 orelse,
                 ..
             } => {
-                self.scan_expression(target)?;
-                self.scan_expression(iter)?;
+                self.scan_expression(target, &ExpressionContext::Store)?;
+                self.scan_expression(iter, &ExpressionContext::Load)?;
                 self.scan_statements(body)?;
                 if let Some(code) = orelse {
                     self.scan_statements(code)?;
                 }
             }
             While { test, body, orelse } => {
-                self.scan_expression(test)?;
+                self.scan_expression(test, &ExpressionContext::Load)?;
                 self.scan_statements(body)?;
                 if let Some(code) = orelse {
                     self.scan_statements(code)?;
@@ -306,51 +385,54 @@ impl SymbolTableBuilder {
                 for name in names {
                     if let Some(alias) = &name.alias {
                         // `import mymodule as myalias`
-                        self.register_name(alias, SymbolRole::Assigned)?;
+                        self.register_name(alias, SymbolUsage::Assigned)?;
                     } else {
                         // `import module`
-                        self.register_name(&name.symbol, SymbolRole::Assigned)?;
+                        self.register_name(
+                            name.symbol.split('.').next().unwrap(),
+                            SymbolUsage::Assigned,
+                        )?;
                     }
                 }
             }
             Return { value } => {
                 if let Some(expression) = value {
-                    self.scan_expression(expression)?;
+                    self.scan_expression(expression, &ExpressionContext::Load)?;
                 }
             }
             Assert { test, msg } => {
-                self.scan_expression(test)?;
+                self.scan_expression(test, &ExpressionContext::Load)?;
                 if let Some(expression) = msg {
-                    self.scan_expression(expression)?;
+                    self.scan_expression(expression, &ExpressionContext::Load)?;
                 }
             }
             Delete { targets } => {
-                self.scan_expressions(targets)?;
+                self.scan_expressions(targets, &ExpressionContext::Delete)?;
             }
             Assign { targets, value } => {
-                self.scan_expressions(targets)?;
-                self.scan_expression(value)?;
+                self.scan_expressions(targets, &ExpressionContext::Store)?;
+                self.scan_expression(value, &ExpressionContext::Load)?;
             }
             AugAssign { target, value, .. } => {
-                self.scan_expression(target)?;
-                self.scan_expression(value)?;
+                self.scan_expression(target, &ExpressionContext::Store)?;
+                self.scan_expression(value, &ExpressionContext::Load)?;
             }
             AnnAssign {
                 target,
                 annotation,
                 value,
             } => {
-                self.scan_expression(target)?;
-                self.scan_expression(annotation)?;
+                self.scan_expression(target, &ExpressionContext::Store)?;
+                self.scan_expression(annotation, &ExpressionContext::Load)?;
                 if let Some(value) = value {
-                    self.scan_expression(value)?;
+                    self.scan_expression(value, &ExpressionContext::Load)?;
                 }
             }
             With { items, body, .. } => {
                 for item in items {
-                    self.scan_expression(&item.context_expr)?;
+                    self.scan_expression(&item.context_expr, &ExpressionContext::Load)?;
                     if let Some(expression) = &item.optional_vars {
-                        self.scan_expression(expression)?;
+                        self.scan_expression(expression, &ExpressionContext::Store)?;
                     }
                 }
                 self.scan_statements(body)?;
@@ -364,10 +446,10 @@ impl SymbolTableBuilder {
                 self.scan_statements(body)?;
                 for handler in handlers {
                     if let Some(expression) = &handler.typ {
-                        self.scan_expression(expression)?;
+                        self.scan_expression(expression, &ExpressionContext::Load)?;
                     }
                     if let Some(name) = &handler.name {
-                        self.register_name(name, SymbolRole::Assigned)?;
+                        self.register_name(name, SymbolUsage::Assigned)?;
                     }
                     self.scan_statements(&handler.body)?;
                 }
@@ -380,95 +462,102 @@ impl SymbolTableBuilder {
             }
             Raise { exception, cause } => {
                 if let Some(expression) = exception {
-                    self.scan_expression(expression)?;
+                    self.scan_expression(expression, &ExpressionContext::Load)?;
                 }
                 if let Some(expression) = cause {
-                    self.scan_expression(expression)?;
+                    self.scan_expression(expression, &ExpressionContext::Load)?;
                 }
             }
         }
         Ok(())
     }
 
-    fn scan_expressions(&mut self, expressions: &[ast::Expression]) -> SymbolTableResult {
+    fn scan_expressions(
+        &mut self,
+        expressions: &[ast::Expression],
+        context: &ExpressionContext,
+    ) -> SymbolTableResult {
         for expression in expressions {
-            self.scan_expression(expression)?;
+            self.scan_expression(expression, context)?;
         }
         Ok(())
     }
 
-    fn scan_expression(&mut self, expression: &ast::Expression) -> SymbolTableResult {
+    fn scan_expression(
+        &mut self,
+        expression: &ast::Expression,
+        context: &ExpressionContext,
+    ) -> SymbolTableResult {
         use ast::ExpressionType::*;
         match &expression.node {
             Binop { a, b, .. } => {
-                self.scan_expression(a)?;
-                self.scan_expression(b)?;
+                self.scan_expression(a, context)?;
+                self.scan_expression(b, context)?;
             }
-            BoolOp { a, b, .. } => {
-                self.scan_expression(a)?;
-                self.scan_expression(b)?;
+            BoolOp { values, .. } => {
+                self.scan_expressions(values, context)?;
             }
             Compare { vals, .. } => {
-                self.scan_expressions(vals)?;
+                self.scan_expressions(vals, context)?;
             }
             Subscript { a, b } => {
-                self.scan_expression(a)?;
-                self.scan_expression(b)?;
+                self.scan_expression(a, context)?;
+                self.scan_expression(b, context)?;
             }
             Attribute { value, .. } => {
-                self.scan_expression(value)?;
+                self.scan_expression(value, context)?;
             }
             Dict { elements } => {
                 for (key, value) in elements {
                     if let Some(key) = key {
-                        self.scan_expression(key)?;
+                        self.scan_expression(key, context)?;
                     } else {
                         // dict unpacking marker
                     }
-                    self.scan_expression(value)?;
+                    self.scan_expression(value, context)?;
                 }
             }
             Await { value } => {
-                self.scan_expression(value)?;
+                self.scan_expression(value, context)?;
             }
             Yield { value } => {
                 if let Some(expression) = value {
-                    self.scan_expression(expression)?;
+                    self.scan_expression(expression, context)?;
                 }
             }
             YieldFrom { value } => {
-                self.scan_expression(value)?;
+                self.scan_expression(value, context)?;
             }
             Unop { a, .. } => {
-                self.scan_expression(a)?;
+                self.scan_expression(a, context)?;
             }
             True | False | None | Ellipsis => {}
             Number { .. } => {}
             Starred { value } => {
-                self.scan_expression(value)?;
+                self.scan_expression(value, context)?;
             }
             Bytes { .. } => {}
             Tuple { elements } | Set { elements } | List { elements } | Slice { elements } => {
-                self.scan_expressions(elements)?;
+                self.scan_expressions(elements, &ExpressionContext::Load)?;
             }
             Comprehension { kind, generators } => {
                 match **kind {
                     ast::ComprehensionKind::GeneratorExpression { ref element }
                     | ast::ComprehensionKind::List { ref element }
                     | ast::ComprehensionKind::Set { ref element } => {
-                        self.scan_expression(element)?;
+                        self.scan_expression(element, &ExpressionContext::Load)?;
                     }
                     ast::ComprehensionKind::Dict { ref key, ref value } => {
-                        self.scan_expression(&key)?;
-                        self.scan_expression(&value)?;
+                        self.scan_expression(&key, &ExpressionContext::Load)?;
+                        self.scan_expression(&value, &ExpressionContext::Load)?;
                     }
                 }
 
                 for generator in generators {
-                    self.scan_expression(&generator.target)?;
-                    self.scan_expression(&generator.iter)?;
+                    self.scan_expression(&generator.target, &ExpressionContext::Store)?;
+                    self.scan_expression(&generator.iter, &ExpressionContext::Load)?;
                     for if_expr in &generator.ifs {
-                        self.scan_expression(if_expr)?;
+                        self.scan_expression(if_expr, &ExpressionContext::Load)?;
                     }
                 }
             }
@@ -477,27 +566,38 @@ impl SymbolTableBuilder {
                 args,
                 keywords,
             } => {
-                self.scan_expression(function)?;
-                self.scan_expressions(args)?;
+                self.scan_expression(function, &ExpressionContext::Load)?;
+                self.scan_expressions(args, &ExpressionContext::Load)?;
                 for keyword in keywords {
-                    self.scan_expression(&keyword.value)?;
+                    self.scan_expression(&keyword.value, &ExpressionContext::Load)?;
                 }
             }
             String { value } => {
                 self.scan_string_group(value)?;
             }
             Identifier { name } => {
-                self.register_name(name, SymbolRole::Used)?;
+                // Determine the contextual usage of this symbol:
+                match context {
+                    ExpressionContext::Delete => {
+                        self.register_name(name, SymbolUsage::Used)?;
+                    }
+                    ExpressionContext::Load => {
+                        self.register_name(name, SymbolUsage::Used)?;
+                    }
+                    ExpressionContext::Store => {
+                        self.register_name(name, SymbolUsage::Assigned)?;
+                    }
+                }
             }
             Lambda { args, body } => {
                 self.enter_function(args)?;
-                self.scan_expression(body)?;
-                self.leave_scope();
+                self.scan_expression(body, &ExpressionContext::Load)?;
+                self.leave_block();
             }
             IfExpression { test, body, orelse } => {
-                self.scan_expression(test)?;
-                self.scan_expression(body)?;
-                self.scan_expression(orelse)?;
+                self.scan_expression(test, &ExpressionContext::Load)?;
+                self.scan_expression(body, &ExpressionContext::Load)?;
+                self.scan_expression(orelse, &ExpressionContext::Load)?;
             }
         }
         Ok(())
@@ -505,10 +605,10 @@ impl SymbolTableBuilder {
 
     fn enter_function(&mut self, args: &ast::Parameters) -> SymbolTableResult {
         // Evaluate eventual default parameters:
-        self.scan_expressions(&args.defaults)?;
+        self.scan_expressions(&args.defaults, &ExpressionContext::Load)?;
         for kw_default in &args.kw_defaults {
             if let Some(expression) = kw_default {
-                self.scan_expression(&expression)?;
+                self.scan_expression(&expression, &ExpressionContext::Load)?;
             }
         }
 
@@ -522,7 +622,7 @@ impl SymbolTableBuilder {
             self.scan_parameter_annotation(name)?;
         }
 
-        self.enter_scope();
+        self.enter_block();
 
         // Fill scope with parameter names:
         self.scan_parameters(&args.args)?;
@@ -540,7 +640,7 @@ impl SymbolTableBuilder {
         match group {
             ast::StringGroup::Constant { .. } => {}
             ast::StringGroup::FormattedValue { value, .. } => {
-                self.scan_expression(value)?;
+                self.scan_expression(value, &ExpressionContext::Load)?;
             }
             ast::StringGroup::Joined { values } => {
                 for subgroup in values {
@@ -552,22 +652,22 @@ impl SymbolTableBuilder {
     }
 
     #[allow(clippy::single_match)]
-    fn register_name(&mut self, name: &str, role: SymbolRole) -> SymbolTableResult {
-        let scope_depth = self.scopes.len();
-        let current_scope = self.scopes.last_mut().unwrap();
+    fn register_name(&mut self, name: &str, role: SymbolUsage) -> SymbolTableResult {
+        let scope_depth = self.tables.len();
+        let table = self.tables.last_mut().unwrap();
         let location = Default::default();
 
         // Some checks:
-        if current_scope.symbols.contains_key(name) {
+        if table.symbols.contains_key(name) {
             // Role already set..
             match role {
-                SymbolRole::Global => {
+                SymbolUsage::Global => {
                     return Err(SymbolTableError {
                         error: format!("name '{}' is used prior to global declaration", name),
                         location,
                     })
                 }
-                SymbolRole::Nonlocal => {
+                SymbolUsage::Nonlocal => {
                     return Err(SymbolTableError {
                         error: format!("name '{}' is used prior to nonlocal declaration", name),
                         location,
@@ -581,7 +681,7 @@ impl SymbolTableBuilder {
 
         // Some more checks:
         match role {
-            SymbolRole::Nonlocal => {
+            SymbolUsage::Nonlocal => {
                 if scope_depth < 2 {
                     return Err(SymbolTableError {
                         error: format!("cannot define nonlocal '{}' at top level.", name),
@@ -595,25 +695,38 @@ impl SymbolTableBuilder {
         }
 
         // Insert symbol when required:
-        if !current_scope.symbols.contains_key(name) {
+        if !table.symbols.contains_key(name) {
             let symbol = Symbol::new(name);
-            current_scope.symbols.insert(name.to_string(), symbol);
+            table.symbols.insert(name.to_string(), symbol);
         }
 
         // Set proper flags on symbol:
-        let symbol = current_scope.symbols.get_mut(name).unwrap();
+        let symbol = table.symbols.get_mut(name).unwrap();
         match role {
-            SymbolRole::Nonlocal => {
-                symbol.is_nonlocal = true;
+            SymbolUsage::Nonlocal => {
+                if let SymbolScope::Unknown = symbol.scope {
+                    symbol.scope = SymbolScope::Nonlocal;
+                } else {
+                    return Err(SymbolTableError {
+                        error: format!("Symbol {} scope cannot be set to nonlocal, since its scope was already determined otherwise.", name),
+                        location,
+                    });
+                }
             }
-            SymbolRole::Assigned => {
+            SymbolUsage::Parameter | SymbolUsage::Assigned => {
                 symbol.is_assigned = true;
-                // symbol.is_local = true;
             }
-            SymbolRole::Global => {
-                symbol.is_global = true;
+            SymbolUsage::Global => {
+                if let SymbolScope::Unknown = symbol.scope {
+                    symbol.scope = SymbolScope::Global;
+                } else {
+                    return Err(SymbolTableError {
+                        error: format!("Symbol {} scope cannot be set to global, since its scope was already determined otherwise.", name),
+                        location,
+                    });
+                }
             }
-            SymbolRole::Used => {
+            SymbolUsage::Used => {
                 symbol.is_referenced = true;
             }
         }
diff --git a/crawl_sourcecode.py b/crawl_sourcecode.py
index bdb7a15b0..33708edbf 100644
--- a/crawl_sourcecode.py
+++ b/crawl_sourcecode.py
@@ -12,6 +12,7 @@ $ diff cpython.txt rustpython.txt
 import ast
 import sys
 import symtable
+import dis
 
 filename = sys.argv[1]
 print('Crawling file:', filename)
@@ -67,3 +68,9 @@ def print_table(table, indent=0):
 
 table = symtable.symtable(source, 'a', 'exec')
 print_table(table)
+
+print()
+print('======== dis.dis ========')
+print()
+co = compile(source, filename, 'exec')
+print(dis.dis(co))
diff --git a/derive/src/compile_bytecode.rs b/derive/src/compile_bytecode.rs
index cfa87163e..cf772fe28 100644
--- a/derive/src/compile_bytecode.rs
+++ b/derive/src/compile_bytecode.rs
@@ -41,7 +41,7 @@ impl CompilationSource {
     fn compile_string(
         &self,
         source: &str,
-        mode: &compile::Mode,
+        mode: compile::Mode,
         module_name: String,
     ) -> Result<CodeObject, Diagnostic> {
         compile::compile(source, mode, module_name, 0)
@@ -50,7 +50,7 @@ impl CompilationSource {
 
     fn compile(
         &self,
-        mode: &compile::Mode,
+        mode: compile::Mode,
         module_name: String,
     ) -> Result<HashMap<String, FrozenModule>, Diagnostic> {
         Ok(match &self.kind {
@@ -94,7 +94,7 @@ impl CompilationSource {
         &self,
         path: &Path,
         parent: String,
-        mode: &compile::Mode,
+        mode: compile::Mode,
     ) -> Result<HashMap<String, FrozenModule>, Diagnostic> {
         let mut code_map = HashMap::new();
         let paths = fs::read_dir(&path).map_err(|err| {
@@ -169,15 +169,13 @@ impl PyCompileInput {
         for meta in &self.metas {
             if let Meta::NameValue(name_value) = meta {
                 if name_value.ident == "mode" {
-                    mode = Some(match &name_value.lit {
-                        Lit::Str(s) => match s.value().as_str() {
-                            "exec" => compile::Mode::Exec,
-                            "eval" => compile::Mode::Eval,
-                            "single" => compile::Mode::Single,
-                            _ => bail_span!(s, "mode must be exec, eval, or single"),
+                    match &name_value.lit {
+                        Lit::Str(s) => match s.value().parse() {
+                            Ok(mode_val) => mode = Some(mode_val),
+                            Err(e) => bail_span!(s, "{}", e),
                         },
                         _ => bail_span!(name_value.lit, "mode must be a string"),
-                    })
+                    }
                 } else if name_value.ident == "module_name" {
                     module_name = Some(match &name_value.lit {
                         Lit::Str(s) => s.value(),
@@ -225,7 +223,7 @@ impl PyCompileInput {
                 )
             })?
             .compile(
-                &mode.unwrap_or(compile::Mode::Exec),
+                mode.unwrap_or(compile::Mode::Exec),
                 module_name.unwrap_or_else(|| "frozen".to_string()),
             )
     }
diff --git a/derive/src/pyclass.rs b/derive/src/pyclass.rs
index c16304d17..f4f0ec255 100644
--- a/derive/src/pyclass.rs
+++ b/derive/src/pyclass.rs
@@ -424,10 +424,12 @@ pub fn impl_pystruct_sequence(attr: AttributeArgs, item: Item) -> Result<TokenSt
                 vm: &::rustpython_vm::vm::VirtualMachine,
                 cls: ::rustpython_vm::obj::objtype::PyClassRef,
             ) -> ::rustpython_vm::pyobject::PyResult<::rustpython_vm::obj::objtuple::PyTupleRef> {
-                let tuple: ::rustpython_vm::obj::objtuple::PyTuple =
-                    vec![#(::rustpython_vm::pyobject::IntoPyObject
-                                ::into_pyobject(self.#field_names, vm)?
-                         ),*].into();
+                let tuple = ::rustpython_vm::obj::objtuple::PyTuple::from(
+                    vec![#(::rustpython_vm::pyobject::IntoPyObject::into_pyobject(
+                        ::std::clone::Clone::clone(&self.#field_names),
+                        vm,
+                    )?),*],
+                );
                 ::rustpython_vm::pyobject::PyValue::into_ref_with_type(tuple, vm, cls)
             }
         }
diff --git a/examples/dis.rs b/examples/dis.rs
new file mode 100644
index 000000000..49fda5760
--- /dev/null
+++ b/examples/dis.rs
@@ -0,0 +1,92 @@
+/// This an example usage of the rustpython_compiler crate.
+/// This program reads, parses, and compiles a file you provide
+/// to RustPython bytecode, and then displays the output in the
+/// `dis.dis` format.
+///
+/// example usage:
+/// $ cargo run --release --example dis demo*.py
+
+#[macro_use]
+extern crate clap;
+extern crate env_logger;
+#[macro_use]
+extern crate log;
+
+use clap::{App, Arg};
+
+use rustpython_compiler::compile;
+use std::error::Error;
+use std::fs;
+use std::path::Path;
+
+fn main() {
+    env_logger::init();
+    let app = App::new("dis")
+        .version(crate_version!())
+        .author(crate_authors!())
+        .about("Compiles and disassembles python script files for viewing their bytecode.")
+        .arg(
+            Arg::with_name("scripts")
+                .help("Scripts to scan")
+                .multiple(true)
+                .required(true),
+        )
+        .arg(
+            Arg::with_name("mode")
+                .help("The mode to compile the scripts in")
+                .long("mode")
+                .short("m")
+                .default_value("exec")
+                .possible_values(&["exec", "single", "eval"])
+                .takes_value(true),
+        )
+        .arg(
+            Arg::with_name("no_expand")
+                .help(
+                    "Don't expand CodeObject LoadConst instructions to show \
+                     the instructions inside",
+                )
+                .long("no-expand")
+                .short("x"),
+        )
+        .arg(
+            Arg::with_name("optimize")
+                .help("The amount of optimization to apply to the compiled bytecode")
+                .short("O")
+                .multiple(true),
+        );
+    let matches = app.get_matches();
+
+    let mode = matches.value_of_lossy("mode").unwrap().parse().unwrap();
+    let expand_codeobjects = !matches.is_present("no_expand");
+    let optimize = matches.occurrences_of("optimize") as u8;
+    let scripts = matches.values_of_os("scripts").unwrap();
+
+    for script in scripts.map(Path::new) {
+        if script.exists() && script.is_file() {
+            let res = display_script(script, mode, optimize, expand_codeobjects);
+            if let Err(e) = res {
+                error!("Error while compiling {:?}: {}", script, e);
+            }
+        } else {
+            eprintln!("{:?} is not a file.", script);
+        }
+    }
+}
+
+fn display_script(
+    path: &Path,
+    mode: compile::Mode,
+    optimize: u8,
+    expand_codeobjects: bool,
+) -> Result<(), Box<dyn Error>> {
+    let source = fs::read_to_string(path)?;
+    let code = compile::compile(&source, mode, path.to_string_lossy().into_owned(), optimize)?;
+    println!("{}:", path.display());
+    if expand_codeobjects {
+        println!("{}", code.display_expand_codeobjects());
+    } else {
+        println!("{}", code);
+    }
+    Ok(())
+}
diff --git a/examples/parse_folder.rs b/examples/parse_folder.rs
index 513333b95..ad0c5f859 100644
--- a/examples/parse_folder.rs
+++ b/examples/parse_folder.rs
@@ -14,8 +14,8 @@ extern crate log;
 use clap::{App, Arg};
 
 use rustpython_parser::{ast, parser};
-use std::path::{Path, PathBuf};
-use std::time::Instant;
+use std::path::Path;
+use std::time::{Duration, Instant};
 
 fn main() {
     env_logger::init();
@@ -61,30 +61,45 @@ fn parse_folder(path: &Path) -> std::io::Result<Vec<ParsedFile>> {
         }
 
         if metadata.is_file() && path.extension().and_then(|s| s.to_str()) == Some("py") {
-            let result = parse_python_file(&path);
-            match &result {
+            let parsed_file = parse_python_file(&path);
+            match &parsed_file.result {
                 Ok(_) => {}
                 Err(y) => error!("Erreur in file {:?} {:?}", path, y),
             }
-            res.push(ParsedFile {
-                filename: Box::new(path),
-                result,
-            });
+
+            res.push(parsed_file);
         }
     }
     Ok(res)
 }
 
-fn parse_python_file(filename: &Path) -> ParseResult {
+fn parse_python_file(filename: &Path) -> ParsedFile {
     info!("Parsing file {:?}", filename);
-    let source = std::fs::read_to_string(filename).map_err(|e| e.to_string())?;
-    parser::parse_program(&source).map_err(|e| e.to_string())
+    match std::fs::read_to_string(filename) {
+        Err(e) => ParsedFile {
+            // filename: Box::new(filename.to_path_buf()),
+            // code: "".to_string(),
+            num_lines: 0,
+            result: Err(e.to_string()),
+        },
+        Ok(source) => {
+            let num_lines = source.to_string().lines().count();
+            let result = parser::parse_program(&source).map_err(|e| e.to_string());
+            ParsedFile {
+                // filename: Box::new(filename.to_path_buf()),
+                // code: source.to_string(),
+                num_lines,
+                result,
+            }
+        }
+    }
 }
 
 fn statistics(results: ScanResult) {
     // println!("Processed {:?} files", res.len());
     println!("Scanned a total of {} files", results.parsed_files.len());
-    let total = results.parsed_files.len();
+    let total: usize = results.parsed_files.len();
+    let total_lines: usize = results.parsed_files.iter().map(|p| p.num_lines).sum();
     let failed = results
         .parsed_files
         .iter()
@@ -103,9 +118,19 @@ fn statistics(results: ScanResult) {
     let duration = results.t2 - results.t1;
     println!("Total time spend: {:?}", duration);
     println!(
-        "File processing rate: {} files/second",
-        (total * 1_000_000) as f64 / duration.as_micros() as f64
+        "Processed {} files. That's {} files/second",
+        total,
+        rate(total, duration)
     );
+    println!(
+        "Processed {} lines of python code. That's {} lines/second",
+        total_lines,
+        rate(total_lines, duration)
+    );
+}
+
+fn rate(counter: usize, duration: Duration) -> f64 {
+    (counter * 1_000_000) as f64 / duration.as_micros() as f64
 }
 
 struct ScanResult {
@@ -115,7 +140,9 @@ struct ScanResult {
 }
 
 struct ParsedFile {
-    filename: Box<PathBuf>,
+    // filename: Box<PathBuf>,
+    // code: String,
+    num_lines: usize,
     result: ParseResult,
 }
 
diff --git a/parser/src/ast.rs b/parser/src/ast.rs
index b11e0f9c6..dc7b2a14d 100644
--- a/parser/src/ast.rs
+++ b/parser/src/ast.rs
@@ -148,9 +148,8 @@ pub type Expression = Located<ExpressionType>;
 #[derive(Debug, PartialEq)]
 pub enum ExpressionType {
     BoolOp {
-        a: Box<Expression>,
         op: BooleanOperator,
-        b: Box<Expression>,
+        values: Vec<Expression>,
     },
     Binop {
         a: Box<Expression>,
diff --git a/parser/src/lexer.rs b/parser/src/lexer.rs
index ae83a1d8d..0f2e28bd2 100644
--- a/parser/src/lexer.rs
+++ b/parser/src/lexer.rs
@@ -340,18 +340,7 @@ where
 
     /// Lex a hex/octal/decimal/binary number without a decimal point.
     fn lex_number_radix(&mut self, start_pos: Location, radix: u32) -> LexResult {
-        let mut value_text = String::new();
-
-        loop {
-            if let Some(c) = self.take_number(radix) {
-                value_text.push(c);
-            } else if self.chr0 == Some('_') {
-                self.next_char();
-            } else {
-                break;
-            }
-        }
-
+        let value_text = self.radix_run(radix);
         let end_pos = self.get_pos();
         let value = BigInt::from_str_radix(&value_text, radix).map_err(|e| LexicalError {
             error: LexicalErrorType::OtherError(format!("{:?}", e)),
@@ -360,24 +349,19 @@ where
         Ok((start_pos, Tok::Int { value }, end_pos))
     }
 
+    /// Lex a normal number, that is, no octal, hex or binary number.
     fn lex_normal_number(&mut self) -> LexResult {
         let start_pos = self.get_pos();
 
-        let mut value_text = String::new();
-
         // Normal number:
-        while let Some(c) = self.take_number(10) {
-            value_text.push(c);
-        }
+        let mut value_text = self.radix_run(10);
 
         // If float:
         if self.chr0 == Some('.') || self.at_exponent() {
             // Take '.':
             if self.chr0 == Some('.') {
                 value_text.push(self.next_char().unwrap());
-                while let Some(c) = self.take_number(10) {
-                    value_text.push(c);
-                }
+                value_text.push_str(&self.radix_run(10));
             }
 
             // 1e6 for example:
@@ -389,9 +373,7 @@ where
                     value_text.push(self.next_char().unwrap());
                 }
 
-                while let Some(c) = self.take_number(10) {
-                    value_text.push(c);
-                }
+                value_text.push_str(&self.radix_run(10));
             }
 
             let value = f64::from_str(&value_text).unwrap();
@@ -426,6 +408,57 @@ where
         }
     }
 
+    /// Consume a sequence of numbers with the given radix,
+    /// the digits can be decorated with underscores
+    /// like this: '1_2_3_4' == '1234'
+    fn radix_run(&mut self, radix: u32) -> String {
+        let mut value_text = String::new();
+        loop {
+            if let Some(c) = self.take_number(radix) {
+                value_text.push(c);
+            } else if self.chr0 == Some('_') && Lexer::<T>::is_digit_of_radix(self.chr1, radix) {
+                self.next_char();
+            } else {
+                break;
+            }
+        }
+        value_text
+    }
+
+    /// Consume a single character with the given radix.
+    fn take_number(&mut self, radix: u32) -> Option<char> {
+        let take_char = Lexer::<T>::is_digit_of_radix(self.chr0, radix);
+
+        if take_char {
+            Some(self.next_char().unwrap())
+        } else {
+            None
+        }
+    }
+
+    /// Test if a digit is of a certain radix.
+    fn is_digit_of_radix(c: Option<char>, radix: u32) -> bool {
+        match radix {
+            2 => match c {
+                Some('0'..='1') => true,
+                _ => false,
+            },
+            8 => match c {
+                Some('0'..='7') => true,
+                _ => false,
+            },
+            10 => match c {
+                Some('0'..='9') => true,
+                _ => false,
+            },
+            16 => match c {
+                Some('0'..='9') | Some('a'..='f') | Some('A'..='F') => true,
+                _ => false,
+            },
+            x => unimplemented!("Radix not implemented: {}", x),
+        }
+    }
+
     /// Test if we face '[eE][-+]?[0-9]+'
     fn at_exponent(&self) -> bool {
         match self.chr0 {
@@ -626,34 +659,6 @@ where
         }
     }
 
-    fn take_number(&mut self, radix: u32) -> Option<char> {
-        let take_char = match radix {
-            2 => match self.chr0 {
-                Some('0'..='1') => true,
-                _ => false,
-            },
-            8 => match self.chr0 {
-                Some('0'..='7') => true,
-                _ => false,
-            },
-            10 => match self.chr0 {
-                Some('0'..='9') => true,
-                _ => false,
-            },
-            16 => match self.chr0 {
-                Some('0'..='9') | Some('a'..='f') | Some('A'..='F') => true,
-                _ => false,
-            },
-            x => unimplemented!("Radix not implemented: {}", x),
-        };
-
-        if take_char {
-            Some(self.next_char().unwrap())
-        } else {
-            None
-        }
-    }
-
     /// This is the main entry point. Call this function to retrieve the next token.
     /// This function is used by the iterator implementation.
     fn inner_next(&mut self) -> LexResult {
diff --git a/parser/src/python.lalrpop b/parser/src/python.lalrpop
index 6af9fea61..968b6c88d 100644
--- a/parser/src/python.lalrpop
+++ b/parser/src/python.lalrpop
@@ -247,7 +247,7 @@ ImportDots: usize = {
 
 ImportAsNames: Vec<ast::ImportSymbol> = {
     <i:OneOrMore<ImportAsAlias<Identifier>>> => i,
-    "(" <i:OneOrMore<ImportAsAlias<Identifier>>> ")" => i,
+    "(" <i:OneOrMore<ImportAsAlias<Identifier>>> ","? ")" => i,
     "*" => {
         // Star import all
         vec![ast::ImportSymbol { symbol: "*".to_string(), alias: None }]
@@ -659,18 +659,32 @@ LambdaDef: ast::Expression = {
 }
 
 OrTest: ast::Expression = {
-    AndTest,
-    <e1:OrTest> <location:@L> "or" <e2:AndTest> => ast::Expression {
-        location,
-        node: ast::ExpressionType::BoolOp { a: Box::new(e1), op: ast::BooleanOperator::Or, b: Box::new(e2) }
+    <e1:AndTest> <location:@L> <e2:("or" AndTest)*> => {
+        if e2.is_empty() {
+            e1
+        } else {
+            let mut values = vec![e1];
+            values.extend(e2.into_iter().map(|e| e.1));
+            ast::Expression {
+                location,
+                node: ast::ExpressionType::BoolOp { op: ast::BooleanOperator::Or, values }
+            }
+        }
     },
 };
 
 AndTest: ast::Expression = {
-    NotTest,
-    <e1:AndTest> <location:@L> "and" <e2:NotTest> => ast::Expression {
-        location,
-        node: ast::ExpressionType::BoolOp { a: Box::new(e1), op: ast::BooleanOperator::And, b: Box::new(e2) }
+    <e1:NotTest> <location:@L> <e2:("and" NotTest)*> => {
+        if e2.is_empty() {
+            e1
+        } else {
+            let mut values = vec![e1];
+            values.extend(e2.into_iter().map(|e| e.1));
+            ast::Expression {
+                location,
+                node: ast::ExpressionType::BoolOp { op: ast::BooleanOperator::And, values }
+            }
+        }
     },
 };
 
@@ -952,11 +966,11 @@ Atom: ast::Expression = {
 };
 
 ListLiteralValues: Vec<ast::Expression> = {
-    <e:OneOrMore<TestOrStarExpr>> <_trailing_comma:","?> => e,
+    <e:OneOrMore<TestOrStarExpr>> ","? => e,
 };
 
 DictLiteralValues: Vec<(Option<ast::Expression>, ast::Expression)> = {
-    <elements:OneOrMore<DictElement>> <_trailing_comma:","?> => elements,
+    <elements:OneOrMore<DictElement>> ","? => elements,
 };
 
 DictEntry: (ast::Expression, ast::Expression) = {
diff --git a/redox/comment-cargo.sh b/redox/comment-cargo.sh
new file mode 100755
index 000000000..edb03f51c
--- /dev/null
+++ b/redox/comment-cargo.sh
@@ -0,0 +1,15 @@
+#!/bin/bash
+
+set -e
+
+cargo=${1:-Cargo.toml}
+
+tmpfile=$(mktemp)
+
+awk '
+/REDOX START/{redox=1; print; next}
+/REDOX END/{redox=0}
+{if (redox) print "#", $0; else print}
+' "$cargo" >"$tmpfile"
+
+mv "$tmpfile" "$cargo"
diff --git a/redox/recipe.sh b/redox/recipe.sh
index 2428d9b5f..cdaa6787c 100644
--- a/redox/recipe.sh
+++ b/redox/recipe.sh
@@ -1,4 +1,5 @@
 GIT=https://github.com/RustPython/RustPython
+BRANCH=redox-release
 CARGOFLAGS=--no-default-features
 export BUILDTIME_RUSTPYTHONPATH=/lib/rustpython/
 
diff --git a/redox/uncomment-cargo.sh b/redox/uncomment-cargo.sh
new file mode 100755
index 000000000..1cc19ca47
--- /dev/null
+++ b/redox/uncomment-cargo.sh
@@ -0,0 +1,15 @@
+#!/bin/bash
+
+set -e
+
+cargo=${1:-Cargo.toml}
+
+tmpfile=$(mktemp)
+
+awk '
+/REDOX START/{redox=1; print; next}
+/REDOX END/{redox=0}
+{if (redox) sub(/^#\s*/, ""); print}
+' "$cargo" >"$tmpfile"
+
+mv "$tmpfile" "$cargo"
diff --git a/src/main.rs b/src/main.rs
index be256572c..899188d04 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -312,11 +312,20 @@ fn run_rustpython(vm: &VirtualMachine, matches: &ArgMatches) -> PyResult<()> {
     }
 
     let scope = vm.new_scope_with_builtins();
-    let main_module = vm.ctx.new_module("__main__", scope.globals.clone());
+    let main_module = vm.new_module("__main__", scope.globals.clone());
 
     vm.get_attribute(vm.sys_module.clone(), "modules")?
         .set_item("__main__", main_module, vm)?;
 
+    let site_result = vm.import("site", &vm.ctx.new_tuple(vec![]), 0);
+
+    if site_result.is_err() {
+        warn!(
+            "Failed to import site, consider adding the Lib directory to your RUSTPYTHONPATH \
+             environment variable",
+        );
+    }
+
     // Figure out if a -c option was given:
     if let Some(command) = matches.value_of("c") {
         run_command(&vm, scope, command.to_string())?;
@@ -333,7 +342,7 @@ fn run_rustpython(vm: &VirtualMachine, matches: &ArgMatches) -> PyResult<()> {
 
 fn _run_string(vm: &VirtualMachine, scope: Scope, source: &str, source_path: String) -> PyResult {
     let code_obj = vm
-        .compile(source, &compile::Mode::Exec, source_path.clone())
+        .compile(source, compile::Mode::Exec, source_path.clone())
         .map_err(|err| vm.new_syntax_error(&err))?;
     // trace!("Code object: {:?}", code_obj.borrow());
     scope
@@ -359,7 +368,7 @@ fn run_module(vm: &VirtualMachine, module: &str) -> PyResult<()> {
     debug!("Running module {}", module);
     let runpy = vm.import("runpy", &vm.ctx.new_tuple(vec![]), 0)?;
     let run_module_as_main = vm.get_attribute(runpy, "_run_module_as_main")?;
-    vm.invoke(run_module_as_main, vec![vm.new_str(module.to_owned())])?;
+    vm.invoke(&run_module_as_main, vec![vm.new_str(module.to_owned())])?;
     Ok(())
 }
 
@@ -426,7 +435,7 @@ fn test_run_script() {
 }
 
 fn shell_exec(vm: &VirtualMachine, source: &str, scope: Scope) -> Result<(), CompileError> {
-    match vm.compile(source, &compile::Mode::Single, "<stdin>".to_string()) {
+    match vm.compile(source, compile::Mode::Single, "<stdin>".to_string()) {
         Ok(code) => {
             match vm.run_code_obj(code, scope.clone()) {
                 Ok(value) => {
diff --git a/tests/snippets/builtin_complex.py b/tests/snippets/builtin_complex.py
index 64b4570c1..f751a95a5 100644
--- a/tests/snippets/builtin_complex.py
+++ b/tests/snippets/builtin_complex.py
@@ -145,3 +145,7 @@ assert '(1+1j)' == str(1+1j)
 assert '(1-1j)' == str(1-1j)
 assert '(1+1j)' == repr(1+1j)
 assert '(1-1j)' == repr(1-1j)
+
+# __getnewargs__
+assert (3 + 5j).__getnewargs__() == (3.0, 5.0)
+assert (5j).__getnewargs__() == (0.0, 5.0)
\ No newline at end of file
diff --git a/tests/snippets/builtin_divmod.py b/tests/snippets/builtin_divmod.py
index 939e1d2d4..ce9bdfba8 100644
--- a/tests/snippets/builtin_divmod.py
+++ b/tests/snippets/builtin_divmod.py
@@ -3,6 +3,7 @@ from testutils import assert_raises
 assert divmod(11, 3) == (3, 2)
 assert divmod(8,11) == (0, 8)
 assert divmod(0.873, 0.252) == (3.0, 0.11699999999999999)
+assert divmod(-86340, 86400) == (-1, 60)
 
 assert_raises(ZeroDivisionError, lambda: divmod(5, 0), 'divmod by zero')
 assert_raises(ZeroDivisionError, lambda: divmod(5.0, 0.0), 'divmod by zero')
diff --git a/tests/snippets/builtin_round.py b/tests/snippets/builtin_round.py
new file mode 100644
index 000000000..6d116b307
--- /dev/null
+++ b/tests/snippets/builtin_round.py
@@ -0,0 +1,21 @@
+from testutils import assertRaises
+
+assert round(0) == 0
+assert isinstance(round(0), int)
+assert round(0.0) == 0
+assert isinstance(round(0.0), int)
+
+assert round(0, None) == 0
+assert isinstance(round(0, None), int)
+assert round(0.0, None) == 0
+assert isinstance(round(0, None), int)
+
+assert round(0, 0) == 0
+assert isinstance(round(0, 0), int)
+assert round(0.0, 0) == 0.0  # Cannot check the type
+assert isinstance(round(0.0, 0), float)
+
+with assertRaises(TypeError):
+    round(0, 0.0)
+with assertRaises(TypeError):
+    round(0.0, 0.0)
diff --git a/tests/snippets/class.py b/tests/snippets/class.py
index 389c22712..1570df360 100644
--- a/tests/snippets/class.py
+++ b/tests/snippets/class.py
@@ -155,3 +155,12 @@ assert T4.t1.__doc__ == "t1"
 
 cm = classmethod(lambda cls: cls)
 assert cm.__func__(int) is int
+
+assert str(super(int, 5)) == "<super: <class 'int'>, <int object>>"
+
+class T5(int):
+    pass
+
+assert str(super(int, T5(5))) == "<super: <class 'int'>, <T5 object>>"
+
+#assert str(super(type, None)) == "<super: <class 'type'>, NULL>"
diff --git a/tests/snippets/ellipsis.py b/tests/snippets/ellipsis.py
index 20bb3a33c..5316b9f86 100644
--- a/tests/snippets/ellipsis.py
+++ b/tests/snippets/ellipsis.py
@@ -11,6 +11,23 @@ assert b is c
 assert b is d
 assert d is e
 
+assert Ellipsis.__repr__() == 'Ellipsis'
+assert Ellipsis.__reduce__() == 'Ellipsis'
+assert type(Ellipsis).__new__(type(Ellipsis)) == Ellipsis
+assert type(Ellipsis).__reduce__(Ellipsis) == 'Ellipsis'
+try:
+    type(Ellipsis).__new__(type(1))
+except TypeError:
+    pass
+else:
+    assert False, '`Ellipsis.__new__` should only accept `type(Ellipsis)` as argument'
+try:
+    type(Ellipsis).__reduce__(1)
+except TypeError:
+    pass
+else:
+    assert False, '`Ellipsis.__reduce__` should only accept `Ellipsis` as argument'
+
 assert Ellipsis is ...
 Ellipsis = 2
 assert Ellipsis is not ...
diff --git a/tests/snippets/floats.py b/tests/snippets/floats.py
index 0200e5a36..6139295f4 100644
--- a/tests/snippets/floats.py
+++ b/tests/snippets/floats.py
@@ -151,12 +151,20 @@ assert float(1.2) == 1.2
 assert math.trunc(1.2) == 1
 assert_raises(OverflowError, float('inf').__trunc__)
 assert_raises(ValueError, float('nan').__trunc__)
-assert 0.5.__round__() == 0.0
-assert 1.5.__round__() == 2.0
+assert isinstance(0.5.__round__(), int)
+assert isinstance(1.5.__round__(), int)
+assert 0.5.__round__() == 0
+assert 1.5.__round__() == 2
+assert isinstance(0.5.__round__(0), float)
+assert isinstance(1.5.__round__(0), float)
 assert 0.5.__round__(0) == 0.0
 assert 1.5.__round__(0) == 2.0
-assert 0.5.__round__(None) == 0.0
-assert 1.5.__round__(None) == 2.0
+assert isinstance(0.5.__round__(None), int)
+assert isinstance(1.5.__round__(None), int)
+assert 0.5.__round__(None) == 0
+assert 1.5.__round__(None) == 2
+assert_raises(TypeError, lambda: 0.5.__round__(0.0))
+assert_raises(TypeError, lambda: 1.5.__round__(0.0))
 assert_raises(OverflowError, float('inf').__round__)
 assert_raises(ValueError, float('nan').__round__)
 
diff --git a/tests/snippets/function.py b/tests/snippets/function.py
index b499c6776..59fd028ea 100644
--- a/tests/snippets/function.py
+++ b/tests/snippets/function.py
@@ -1,4 +1,3 @@
-
 __name__ = "function"
 
 
@@ -72,3 +71,20 @@ def f6():
 
 
 f6()
+
+
+def f7():
+    try:
+        def t() -> void: # noqa: F821
+            pass
+    except NameError:
+        return True
+    return False
+
+assert f7()
+
+
+def f8() -> int:
+    return 10
+
+assert f8() == 10
diff --git a/tests/snippets/imghdrdata/python.bmp b/tests/snippets/imghdrdata/python.bmp
new file mode 100644
index 000000000..675f95191
Binary files /dev/null and b/tests/snippets/imghdrdata/python.bmp differ
diff --git a/tests/snippets/imghdrdata/python.exr b/tests/snippets/imghdrdata/python.exr
new file mode 100644
index 000000000..773c81ee1
Binary files /dev/null and b/tests/snippets/imghdrdata/python.exr differ
diff --git a/tests/snippets/imghdrdata/python.gif b/tests/snippets/imghdrdata/python.gif
new file mode 100644
index 000000000..96fd9fef7
Binary files /dev/null and b/tests/snippets/imghdrdata/python.gif differ
diff --git a/tests/snippets/imghdrdata/python.jpg b/tests/snippets/imghdrdata/python.jpg
new file mode 100644
index 000000000..21222c09f
Binary files /dev/null and b/tests/snippets/imghdrdata/python.jpg differ
diff --git a/tests/snippets/imghdrdata/python.pbm b/tests/snippets/imghdrdata/python.pbm
new file mode 100644
index 000000000..1848ba7ff
--- /dev/null
+++ b/tests/snippets/imghdrdata/python.pbm
@@ -0,0 +1,3 @@
+P4
+16 16
+ûñ¿úßÕ­±[ñ¥a_ÁX
°
°
ðððð?ÿÿ
\ No newline at end of file
diff --git a/tests/snippets/imghdrdata/python.pgm b/tests/snippets/imghdrdata/python.pgm
new file mode 100644
index 000000000..8349f2a53
Binary files /dev/null and b/tests/snippets/imghdrdata/python.pgm differ
diff --git a/tests/snippets/imghdrdata/python.png b/tests/snippets/imghdrdata/python.png
new file mode 100644
index 000000000..1a987f79f
Binary files /dev/null and b/tests/snippets/imghdrdata/python.png differ
diff --git a/tests/snippets/imghdrdata/python.ppm b/tests/snippets/imghdrdata/python.ppm
new file mode 100644
index 000000000..7d9cdb321
Binary files /dev/null and b/tests/snippets/imghdrdata/python.ppm differ
diff --git a/tests/snippets/imghdrdata/python.ras b/tests/snippets/imghdrdata/python.ras
new file mode 100644
index 000000000..130e96f81
Binary files /dev/null and b/tests/snippets/imghdrdata/python.ras differ
diff --git a/tests/snippets/imghdrdata/python.sgi b/tests/snippets/imghdrdata/python.sgi
new file mode 100644
index 000000000..ffe9081c7
Binary files /dev/null and b/tests/snippets/imghdrdata/python.sgi differ
diff --git a/tests/snippets/imghdrdata/python.tiff b/tests/snippets/imghdrdata/python.tiff
new file mode 100644
index 000000000..39d0bfcec
Binary files /dev/null and b/tests/snippets/imghdrdata/python.tiff differ
diff --git a/tests/snippets/imghdrdata/python.webp b/tests/snippets/imghdrdata/python.webp
new file mode 100644
index 000000000..e824ec7fb
Binary files /dev/null and b/tests/snippets/imghdrdata/python.webp differ
diff --git a/tests/snippets/imghdrdata/python.xbm b/tests/snippets/imghdrdata/python.xbm
new file mode 100644
index 000000000..cfbee2e98
--- /dev/null
+++ b/tests/snippets/imghdrdata/python.xbm
@@ -0,0 +1,6 @@
+#define python_width 16
+#define python_height 16
+static char python_bits[] = {
+  0xDF, 0xFE, 0x8F, 0xFD, 0x5F, 0xFB, 0xAB, 0xFE, 0xB5, 0x8D, 0xDA, 0x8F, 
+  0xA5, 0x86, 0xFA, 0x83, 0x1A, 0x80, 0x0D, 0x80, 0x0D, 0x80, 0x0F, 0xE0, 
+  0x0F, 0xF8, 0x0F, 0xF8, 0x0F, 0xFC, 0xFF, 0xFF, };
diff --git a/tests/snippets/ints.py b/tests/snippets/ints.py
index 0b6eb7f76..0e89d44f3 100644
--- a/tests/snippets/ints.py
+++ b/tests/snippets/ints.py
@@ -36,7 +36,17 @@ assert (2).__rsub__(1) == -1
 assert (2).__mul__(1) == 2
 assert (2).__rmul__(1) == 2
 assert (2).__truediv__(1) == 2.0
+with assertRaises(ZeroDivisionError):
+    (2).__truediv__(0)
 assert (2).__rtruediv__(1) == 0.5
+assert (-2).__floordiv__(3) == -1
+with assertRaises(ZeroDivisionError):
+    (2).__floordiv__(0)
+assert (-3).__rfloordiv__(2) == -1
+assert (-2).__divmod__(3) == (-1, 1)
+with assertRaises(ZeroDivisionError):
+    (2).__divmod__(0)
+assert (-3).__rdivmod__(2) == (-1, -1)
 assert (2).__pow__(3) == 8
 assert (10).__pow__(-1) == 0.1
 assert (2).__rpow__(3) == 9
@@ -90,6 +100,10 @@ assert int() == 0
 assert int("101", 2) == 5
 assert int("101", base=2) == 5
 assert int(1) == 1
+assert int(' 1') == 1
+assert int('1 ') == 1
+assert int(' 1 ') == 1
+assert int('10', base=0) == 10
 
 assert int.from_bytes(b'\x00\x10', 'big') == 16
 assert int.from_bytes(b'\x00\x10', 'little') == 4096
@@ -103,6 +117,13 @@ assert (-1024).to_bytes(4, 'little', signed=True) == b'\x00\xfc\xff\xff'
 assert (2147483647).to_bytes(8, 'big', signed=False) == b'\x00\x00\x00\x00\x7f\xff\xff\xff'
 assert (-2147483648).to_bytes(8, 'little', signed=True) == b'\x00\x00\x00\x80\xff\xff\xff\xff'
 
+with assertRaises(ValueError):
+    # check base first
+    int(' 1 ', base=1)
+
+with assertRaises(ValueError):
+    int(' 1 ', base=37)
+
 with assertRaises(TypeError):
     int(base=2)
 
@@ -146,3 +167,16 @@ class F(float):
         return 3
 
 assert int(F(1.2)) == 3
+
+assert isinstance((0).__round__(), int)
+assert isinstance((1).__round__(), int)
+assert (0).__round__() == 0
+assert (1).__round__() == 1
+assert isinstance((0).__round__(0), int)
+assert isinstance((1).__round__(0), int)
+assert (0).__round__(0) == 0
+assert (1).__round__(0) == 1
+assert_raises(TypeError, lambda: (0).__round__(None))
+assert_raises(TypeError, lambda: (1).__round__(None))
+assert_raises(TypeError, lambda: (0).__round__(0.0))
+assert_raises(TypeError, lambda: (1).__round__(0.0))
\ No newline at end of file
diff --git a/tests/snippets/json_snippet.py b/tests/snippets/json_snippet.py
index 15866ab86..d47266b58 100644
--- a/tests/snippets/json_snippet.py
+++ b/tests/snippets/json_snippet.py
@@ -1,5 +1,6 @@
 from testutils import assert_raises
 import json
+from io import StringIO
 
 def round_trip_test(obj):
     # serde_json and Python's json module produce slightly differently spaced
@@ -7,63 +8,129 @@ def round_trip_test(obj):
     # proxy
     return obj == json.loads(json.dumps(obj))
 
+def json_dump(obj):
+    f = StringIO()
+    json.dump(obj, f)
+    f.seek(0)
+    return f.getvalue()
+
+def json_load(obj):
+    f = StringIO(obj)
+    return json.load(f)
+
 assert '"string"' == json.dumps("string")
+assert '"string"' == json_dump("string")
+
 assert "1" == json.dumps(1)
+assert "1" == json_dump(1)
+
 assert "1.0" == json.dumps(1.0)
+assert "1.0" == json_dump(1.0)
+
 assert "true" == json.dumps(True)
+assert "true" == json_dump(True)
+
 assert "false" == json.dumps(False)
+assert "false" == json_dump(False)
+
 assert 'null' == json.dumps(None)
+assert 'null' == json_dump(None)
 
 assert '[]' == json.dumps([])
+assert '[]' == json_dump([])
+
 assert '[1]' == json.dumps([1])
+assert '[1]' == json_dump([1])
+
 assert '[[1]]' == json.dumps([[1]])
+assert '[[1]]' == json_dump([[1]])
+
 assert round_trip_test([1, "string", 1.0, True])
 
 assert '[]' == json.dumps(())
+assert '[]' == json_dump(())
+
 assert '[1]' == json.dumps((1,))
+assert '[1]' == json_dump((1,))
+
 assert '[[1]]' == json.dumps(((1,),))
+assert '[[1]]' == json_dump(((1,),))
 # tuples don't round-trip through json
 assert [1, "string", 1.0, True] == json.loads(json.dumps((1, "string", 1.0, True)))
 
 assert '{}' == json.dumps({})
+assert '{}' == json_dump({})
 assert round_trip_test({'a': 'b'})
 
 # should reject non-str keys in jsons
 assert_raises(json.JSONDecodeError, lambda: json.loads('{3: "abc"}'))
+assert_raises(json.JSONDecodeError, lambda: json_load('{3: "abc"}'))
 
 # should serialize non-str keys as strings
 assert json.dumps({'3': 'abc'}) == json.dumps({3: 'abc'})
 
 assert 1 == json.loads("1")
+assert 1 == json_load("1")
+
 assert -1 == json.loads("-1")
+assert -1 == json_load("-1")
+
 assert 1.0 == json.loads("1.0")
+assert 1.0 == json_load("1.0")
+
 assert -1.0 == json.loads("-1.0")
+assert -1.0 == json_load("-1.0")
+
 assert "str" == json.loads('"str"')
+assert "str" == json_load('"str"')
+
 assert True is json.loads('true')
+assert True is json_load('true')
+
 assert False is json.loads('false')
+assert False is json_load('false')
+
 assert None is json.loads('null')
+assert None is json_load('null')
+
 assert [] == json.loads('[]')
+assert [] == json_load('[]')
+
 assert ['a'] == json.loads('["a"]')
+assert ['a'] == json_load('["a"]')
+
 assert [['a'], 'b'] == json.loads('[["a"], "b"]')
+assert [['a'], 'b'] == json_load('[["a"], "b"]')
 
 class String(str): pass
 
 assert "string" == json.loads(String('"string"'))
+assert "string" == json_load(String('"string"'))
+
 assert '"string"' == json.dumps(String("string"))
+assert '"string"' == json_dump(String("string"))
 
 class Int(int): pass
 class Float(float): pass
 
 assert '1' == json.dumps(Int(1))
+assert '1' == json_dump(Int(1))
+
 assert '0.5' == json.dumps(Float(0.5))
+assert '0.5' == json_dump(Float(0.5))
 
 class List(list): pass
 class Tuple(tuple): pass
 class Dict(dict): pass
 
 assert '[1]' == json.dumps(List([1]))
+assert '[1]' == json_dump(List([1]))
+
 assert json.dumps((1, "string", 1.0, True)) == json.dumps(Tuple((1, "string", 1.0, True)))
+assert json_dump((1, "string", 1.0, True)) == json_dump(Tuple((1, "string", 1.0, True)))
+
 assert json.dumps({'a': 'b'}) == json.dumps(Dict({'a': 'b'}))
+assert json_dump({'a': 'b'}) == json_dump(Dict({'a': 'b'}))
 
 # big ints should not crash VM
 # TODO: test for correct output when actual serialization implemented and doesn’t throw
diff --git a/tests/snippets/math_module.py b/tests/snippets/math_module.py
index 8a6aee0e9..d998f1b89 100644
--- a/tests/snippets/math_module.py
+++ b/tests/snippets/math_module.py
@@ -83,6 +83,13 @@ assert str(math.frexp(0.0)) == str((+0.0, 0))
 assert str(math.frexp(-0.0)) == str((-0.0, 0))
 assert math.frexp(1) == (0.5, 1)
 assert math.frexp(1.5) == (0.75, 1)
+assert_raises(TypeError, lambda: math.frexp(None))
+
+assert str(math.ldexp(+0.0, 0)) == str(0.0)
+assert str(math.ldexp(-0.0, 0)) == str(-0.0)
+assert math.ldexp(0.5, 1) == 1
+assert math.ldexp(0.75, 1) == 1.5
+assert_raises(TypeError, lambda: math.ldexp(None, None))
 
 assert math.frexp(float('inf')) == (float('inf'), 0)
 assert str(math.frexp(float('nan'))) == str((float('nan'), 0))
@@ -97,3 +104,11 @@ assert math.gcd(1, -1) == 1
 assert math.gcd(-1, -1) == 1
 assert math.gcd(125, -255) == 5
 assert_raises(TypeError, lambda: math.gcd(1.1, 2))
+
+assert math.factorial(0) == 1
+assert math.factorial(1) == 1
+assert math.factorial(2) == 2
+assert math.factorial(3) == 6
+assert math.factorial(10) == 3628800
+assert math.factorial(20) == 2432902008176640000
+assert_raises(ValueError, lambda: math.factorial(-1))
diff --git a/tests/snippets/numbers.py b/tests/snippets/numbers.py
index c36602ee1..1e6b03777 100644
--- a/tests/snippets/numbers.py
+++ b/tests/snippets/numbers.py
@@ -1,3 +1,5 @@
+from testutils import assertRaises
+
 x = 5
 x.__init__(6)
 assert x == 5
@@ -36,9 +38,37 @@ assert int(0).__invert__() == -1
 assert int(-3).__invert__() == 2
 assert int(4).__invert__() == -5
 
+assert int(0).__ror__(0) == 0
+assert int(1).__ror__(0) == 1
+assert int(0).__ror__(1) == 1
+assert int(1).__ror__(1) == 1
+assert int(3).__ror__(-3) == -1
+assert int(3).__ror__(4) == 7
+
+assert int(0).__rand__(0) == 0
+assert int(1).__rand__(0) == 0
+assert int(0).__rand__(1) == 0
+assert int(1).__rand__(1) == 1
+assert int(3).__rand__(-3) == 1
+assert int(3).__rand__(4) == 0
+
 assert int(0).__rxor__(0) == 0
 assert int(1).__rxor__(0) == 1
 assert int(0).__rxor__(1) == 1
 assert int(1).__rxor__(1) == 0
 assert int(3).__rxor__(-3) == -2
 assert int(3).__rxor__(4) == 7
+
+assert int(4).__lshift__(1) == 8
+assert int(4).__rshift__(1) == 2
+assert int(4).__rlshift__(1) == 16
+assert int(4).__rrshift__(1) == 0
+
+# Test underscores in numbers:
+assert 1_2 == 12
+assert 1_2_3 == 123
+assert 1_2.3_4 == 12.34
+assert 1_2.3_4e0_0 == 12.34
+
+with assertRaises(SyntaxError):
+    eval('1__2')
diff --git a/tests/snippets/object.py b/tests/snippets/object.py
index 6845a0b3e..663a2cd76 100644
--- a/tests/snippets/object.py
+++ b/tests/snippets/object.py
@@ -7,6 +7,10 @@ myobj = MyObject()
 assert myobj == myobj
 assert not myobj != myobj
 
+object.__subclasshook__() == NotImplemented
+object.__subclasshook__(1) == NotImplemented
+object.__subclasshook__(1, 2) == NotImplemented
+
 assert MyObject().__eq__(MyObject()) == NotImplemented
 assert MyObject().__ne__(MyObject()) == NotImplemented
 assert MyObject().__lt__(MyObject()) == NotImplemented
diff --git a/tests/snippets/property.py b/tests/snippets/property.py
index da2c1ee63..afcfe16ec 100644
--- a/tests/snippets/property.py
+++ b/tests/snippets/property.py
@@ -59,7 +59,11 @@ with assertRaises(AttributeError):
 with assertRaises(TypeError):
     property.__new__(object)
 
-# assert p.__doc__ is None
+assert p.__doc__ is None
+
+# Test property instance __doc__ attribute:
+p.__doc__ = '222'
+assert p.__doc__ == '222'
 
 
 p1 = property("a", "b", "c")
diff --git a/tests/snippets/short_circuit_evaluations.py b/tests/snippets/short_circuit_evaluations.py
new file mode 100644
index 000000000..f83a4137c
--- /dev/null
+++ b/tests/snippets/short_circuit_evaluations.py
@@ -0,0 +1,15 @@
+
+# Test various cases of short circuit evaluation:
+
+run = 1
+timeTaken = 33
+r = (11, 22, run, run != 1 and "s" or "", timeTaken)
+print(r)
+assert r == (11, 22, 1, '', 33)
+
+
+run = 0
+r = (11, 22, run, run != 1 and "s" or "", timeTaken)
+print(r)
+assert r == (11, 22, 0, 's', 33)
+
diff --git a/tests/snippets/stdlib_functools.py b/tests/snippets/stdlib_functools.py
new file mode 100644
index 000000000..bd95f0e81
--- /dev/null
+++ b/tests/snippets/stdlib_functools.py
@@ -0,0 +1,79 @@
+from functools import reduce
+from testutils import assertRaises
+
+class Squares:
+    def __init__(self, max):
+        self.max = max
+        self.sofar = []
+
+    def __len__(self):
+        return len(self.sofar)
+
+    def __getitem__(self, i):
+        if not 0 <= i < self.max: raise IndexError
+        n = len(self.sofar)
+        while n <= i:
+            self.sofar.append(n*n)
+            n += 1
+        return self.sofar[i]
+
+def add(a, b):
+    return a + b
+
+assert reduce(add, ['a', 'b', 'c']) == 'abc'
+assert reduce(add, ['a', 'b', 'c'], str(42)) == '42abc'
+assert reduce(add, [['a', 'c'], [], ['d', 'w']], []) == ['a','c','d','w']
+assert reduce(add, [['a', 'c'], [], ['d', 'w']], []) == ['a','c','d','w']
+assert reduce(lambda x, y: x*y, range(2, 21), 1) == 2432902008176640000
+assert reduce(add, Squares(10)) == 285
+assert reduce(add, Squares(10), 0) == 285
+assert reduce(add, Squares(0), 0) == 0
+assert reduce(42, "1") == "1"
+assert reduce(42, "", "1") == "1"
+
+with assertRaises(TypeError):
+    reduce()
+
+with assertRaises(TypeError):
+    reduce(42, 42)
+
+with assertRaises(TypeError):
+    reduce(42, 42, 42)
+
+class TestFailingIter:
+    def __iter__(self):
+        raise RuntimeError
+
+with assertRaises(RuntimeError):
+    reduce(add, TestFailingIter())
+
+assert reduce(add, [], None) == None
+assert reduce(add, [], 42) == 42
+
+class BadSeq:
+    def __getitem__(self, index):
+        raise ValueError
+with assertRaises(ValueError):
+    reduce(42, BadSeq())
+
+# Test reduce()'s use of iterators.
+class SequenceClass:
+    def __init__(self, n):
+        self.n = n
+    def __getitem__(self, i):
+        if 0 <= i < self.n:
+            return i
+        else:
+            raise IndexError
+
+assert reduce(add, SequenceClass(5)) == 10
+assert reduce(add, SequenceClass(5), 42) == 52
+with assertRaises(TypeError):
+    reduce(add, SequenceClass(0))
+
+assert reduce(add, SequenceClass(0), 42) == 42
+assert reduce(add, SequenceClass(1)) == 0
+assert reduce(add, SequenceClass(1), 42) == 42
+
+d = {"one": 1, "two": 2, "three": 3}
+assert reduce(add, d) == "".join(d.keys())
diff --git a/tests/snippets/stdlib_io.py b/tests/snippets/stdlib_io.py
index 184146081..ea52ad3e9 100644
--- a/tests/snippets/stdlib_io.py
+++ b/tests/snippets/stdlib_io.py
@@ -1,5 +1,6 @@
 from io import BufferedReader, FileIO, StringIO, BytesIO
 import os
+from testutils import assertRaises
 
 fi = FileIO('README.md')
 assert fi.seekable()
@@ -23,3 +24,15 @@ fd = os.open('README.md', os.O_RDONLY)
 with FileIO(fd) as fio:
 	res2 = fio.read()
 	assert res == res2
+
+fi = FileIO('README.md')
+fi.read()
+fi.close()
+with assertRaises(ValueError):
+    fi.read()
+
+with FileIO('README.md') as fio:
+	nres = fio.read(1)
+	assert len(nres) == 1
+	nres = fio.read(2)
+	assert len(nres) == 2
\ No newline at end of file
diff --git a/tests/snippets/stdlib_os.py b/tests/snippets/stdlib_os.py
index e48d4c945..6aa379c98 100644
--- a/tests/snippets/stdlib_os.py
+++ b/tests/snippets/stdlib_os.py
@@ -266,8 +266,6 @@ if "win" not in sys.platform:
     assert isinstance(os.getppid(), int)
     assert isinstance(os.getpgid(os.getpid()), int)
 
-    assert os.getppid() < os.getpid()
-
     if os.getuid() != 0:
         assert_raises(PermissionError, lambda: os.setgid(42))
         assert_raises(PermissionError, lambda: os.setegid(42))
diff --git a/tests/snippets/stdlib_socket.py b/tests/snippets/stdlib_socket.py
index 581100c58..d5727bb25 100644
--- a/tests/snippets/stdlib_socket.py
+++ b/tests/snippets/stdlib_socket.py
@@ -119,6 +119,12 @@ with assertRaises(OSError):
 with assertRaises(OSError):
 	socket.inet_aton("test")
 
+with assertRaises(OverflowError):
+	socket.htonl(-1)
+
+assert socket.htonl(0)==0
+assert socket.htonl(10)==167772160
+
 assert socket.inet_aton("127.0.0.1")==b"\x7f\x00\x00\x01"
 assert socket.inet_aton("255.255.255.255")==b"\xff\xff\xff\xff"
 
@@ -129,3 +135,5 @@ assert socket.inet_ntoa(b"\xff\xff\xff\xff")=="255.255.255.255"
 with assertRaises(OSError):
 	socket.inet_ntoa(b"\xff\xff\xff\xff\xff")
 
+with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+	pass
diff --git a/tests/snippets/stdlib_subprocess.py b/tests/snippets/stdlib_subprocess.py
index fa1f3c30c..9e04f4934 100644
--- a/tests/snippets/stdlib_subprocess.py
+++ b/tests/snippets/stdlib_subprocess.py
@@ -1,6 +1,7 @@
 import subprocess
 import time
 import sys
+import signal
 
 from testutils import assertRaises
 
@@ -27,9 +28,33 @@ assert p.returncode == 0
 p = subprocess.Popen(["echo", "test"], stdout=subprocess.PIPE)
 p.wait()
 
-if "win" not in sys.platform:
+is_unix = "win" not in sys.platform or "darwin" in sys.platform
+
+if is_unix:
 	# unix
-	assert p.stdout.read() == b"test\n"
+	test_output = b"test\n"
 else:
 	# windows
-	assert p.stdout.read() == b"test\r\n"
+	test_output = b"test\r\n"
+
+assert p.stdout.read() == test_output
+
+p = subprocess.Popen(["sleep", "2"])
+p.terminate()
+p.wait()
+if is_unix:
+	assert p.returncode == -signal.SIGTERM
+else:
+	assert p.returncode == 1
+
+p = subprocess.Popen(["sleep", "2"])
+p.kill()
+p.wait()
+if is_unix:
+	assert p.returncode == -signal.SIGKILL
+else:
+	assert p.returncode == 1
+
+p = subprocess.Popen(["echo", "test"], stdout=subprocess.PIPE)
+(stdout, stderr) = p.communicate()
+assert stdout == test_output
diff --git a/tests/snippets/stdlib_zlib.py b/tests/snippets/stdlib_zlib.py
new file mode 100644
index 000000000..42847704a
--- /dev/null
+++ b/tests/snippets/stdlib_zlib.py
@@ -0,0 +1,62 @@
+import zlib
+from testutils import assert_raises
+
+# checksum functions
+assert zlib.crc32(b"123") == 2286445522
+assert zlib.crc32(b"123", 1) == 2307525093
+assert zlib.crc32(b"123", 2) == 2345449404
+assert zlib.crc32(b"123", 3) == 2316230027
+assert zlib.crc32(b"123", 4) == 2403453710
+assert zlib.crc32(b"123", 5) == 2390991161
+assert zlib.crc32(b"123", 6) == 2361728864
+assert zlib.crc32(b"123", -123) == 3515918521
+assert zlib.crc32(b"123", -122) == 3554023136
+assert zlib.crc32(b"123", -121) == 3524558039
+assert zlib.crc32(b"123", -120) == 3645389802
+assert zlib.crc32(b"123", -119) == 3632943581
+assert zlib.crc32(b"123", -118) == 3670863748
+assert zlib.crc32(b"123") == zlib.crc32(b"123", 0)
+
+assert zlib.adler32(b"456") == 20906144
+assert zlib.adler32(b"456", 1) == 20906144
+assert zlib.adler32(b"456", 2) == 21102753
+assert zlib.adler32(b"456", 3) == 21299362
+assert zlib.adler32(b"456", 4) == 21495971
+assert zlib.adler32(b"456", 5) == 21692580
+assert zlib.adler32(b"456", 6) == 21889189
+assert zlib.adler32(b"456", -123) == 393267
+assert zlib.adler32(b"456", -122) == 589876
+assert zlib.adler32(b"456", -121) == 786485
+assert zlib.adler32(b"456", -120) == 983094
+assert zlib.adler32(b"456", -119) == 1179703
+assert zlib.adler32(b"456", -118) == 1376312
+assert zlib.adler32(b"456") == zlib.adler32(b"456", 1)
+
+# compression
+lorem = bytes("Lorem ipsum dolor sit amet", "utf-8")
+
+compressed_lorem_list = [
+    b"x\x01\x01\x1a\x00\xe5\xffLorem ipsum dolor sit amet\x83\xd5\t\xc5",
+    b"x\x01\xf3\xc9/J\xcdU\xc8,(.\xcdUH\xc9\xcf\xc9/R(\xce,QH\xccM-\x01\x00\x83\xd5\t\xc5",
+    b"x^\xf3\xc9/J\xcdU\xc8,(.\xcdUH\xc9\xcf\xc9/R(\xce,QH\xccM-\x01\x00\x83\xd5\t\xc5",
+    b"x^\xf3\xc9/J\xcdU\xc8,(.\xcdUH\xc9\xcf\xc9/R(\xce,QH\xccM-\x01\x00\x83\xd5\t\xc5",
+    b"x^\xf3\xc9/J\xcdU\xc8,(.\xcdUH\xc9\xcf\xc9/R(\xce,QH\xccM-\x01\x00\x83\xd5\t\xc5",
+    b"x^\xf3\xc9/J\xcdU\xc8,(.\xcdUH\xc9\xcf\xc9/R(\xce,QH\xccM-\x01\x00\x83\xd5\t\xc5",
+    b"x\x9c\xf3\xc9/J\xcdU\xc8,(.\xcdUH\xc9\xcf\xc9/R(\xce,QH\xccM-\x01\x00\x83\xd5\t\xc5",
+    b"x\xda\xf3\xc9/J\xcdU\xc8,(.\xcdUH\xc9\xcf\xc9/R(\xce,QH\xccM-\x01\x00\x83\xd5\t\xc5",
+    b"x\xda\xf3\xc9/J\xcdU\xc8,(.\xcdUH\xc9\xcf\xc9/R(\xce,QH\xccM-\x01\x00\x83\xd5\t\xc5",
+    b"x\xda\xf3\xc9/J\xcdU\xc8,(.\xcdUH\xc9\xcf\xc9/R(\xce,QH\xccM-\x01\x00\x83\xd5\t\xc5",
+]
+
+for level, text in enumerate(compressed_lorem_list):
+    assert zlib.compress(lorem, level) == text
+
+# default level
+assert zlib.compress(lorem) == zlib.compress(lorem, -1) == zlib.compress(lorem, 6)
+
+# decompression
+for text in compressed_lorem_list:
+    assert zlib.decompress(text) == lorem
+
+assert_raises(zlib.error, lambda: zlib.compress(b"123", -40))
+assert_raises(zlib.error, lambda: zlib.compress(b"123", 10))
diff --git a/tests/snippets/strings.py b/tests/snippets/strings.py
index ed5bfb972..7b219ba8a 100644
--- a/tests/snippets/strings.py
+++ b/tests/snippets/strings.py
@@ -212,6 +212,13 @@ assert "%(first)s %(second)s" % {'second': 'World!', 'first': "Hello,"} == "Hell
 assert "%(key())s" % {'key()': 'aaa'}
 assert "%s %a %r" % (f, f, f) == "str(Foo) repr(Foo) repr(Foo)"
 assert "repr() shows quotes: %r; str() doesn't: %s" % ("test1", "test2") == "repr() shows quotes: 'test1'; str() doesn't: test2"
+assert "%f" % (1.2345) == "1.234500"
+assert "%+f" % (1.2345) == "+1.234500"
+assert "% f" % (1.2345) == " 1.234500"
+assert "%f" % (-1.2345) == "-1.234500"
+assert "%f" % (1.23456789012) == "1.234568"
+assert "%f" % (123) == "123.000000"
+assert "%f" % (-123) == "-123.000000"
 
 assert_raises(TypeError, lambda: "My name is %s and I'm %(age)d years old" % ("Foo", 25), msg="format requires a mapping")
 assert_raises(TypeError, lambda: "My name is %(name)s" % "Foo", msg="format requires a mapping")
@@ -293,3 +300,6 @@ assert next(str_iter_reversed) == "2"
 assert next(str_iter_reversed) == "1"
 assert next(str_iter_reversed, None) == None
 assert_raises(StopIteration, lambda: next(str_iter_reversed))
+
+assert str.__rmod__('%i', 30) == NotImplemented
+assert_raises(TypeError, lambda: str.__rmod__(30, '%i'))
diff --git a/tests/snippets/test_imghdr.py b/tests/snippets/test_imghdr.py
new file mode 100644
index 000000000..00632f886
--- /dev/null
+++ b/tests/snippets/test_imghdr.py
@@ -0,0 +1,27 @@
+# unittest for modified imghdr.py
+# Should be replace it into https://github.com/python/cpython/blob/master/Lib/test/test_imghdr.py
+import os
+import imghdr
+
+
+TEST_FILES = (
+    #('python.png', 'png'),
+    ('python.gif', 'gif'),
+    ('python.bmp', 'bmp'),
+    ('python.ppm', 'ppm'),
+    ('python.pgm', 'pgm'),
+    ('python.pbm', 'pbm'),
+    ('python.jpg', 'jpeg'),
+    ('python.ras', 'rast'),
+    #('python.sgi', 'rgb'),
+    ('python.tiff', 'tiff'),
+    ('python.xbm', 'xbm'),
+    ('python.webp', 'webp'),
+    ('python.exr', 'exr'),
+)
+
+resource_dir = os.path.join(os.path.dirname(__file__), 'imghdrdata')
+
+for fname, expected in TEST_FILES:
+    res = imghdr.what(os.path.join(resource_dir, fname))
+    assert res == expected
\ No newline at end of file
diff --git a/vm/Cargo.toml b/vm/Cargo.toml
index abe546732..c83de6eb7 100644
--- a/vm/Cargo.toml
+++ b/vm/Cargo.toml
@@ -29,6 +29,7 @@ num-bigint = { version = "0.2", features = ["serde"] }
 num-traits = "=0.2.6"
 num-integer = "=0.1.39"
 num-rational = "0.2.1"
+num-iter = "0.1"
 rand = "0.5"
 log = "0.3"
 rustpython-derive = {path = "../derive", version = "0.1.0"}
@@ -72,5 +73,13 @@ flamer = { version = "0.3", optional = true }
 pwd = "1"
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
+crc32fast = "1.2.0"
+adler32 = "1.0.3"
+flate2 = { version = "1.0", features = ["zlib"], default-features = false }
+libz-sys = "1.0.25"
 gethostname = "0.2.0"
 subprocess = "0.1.18"
+num_cpus = "1.0"
+
+[target."cfg(windows)".dependencies]
+kernel32-sys = "0.2.2"
diff --git a/vm/Lib/_bootstrap_external.py b/vm/Lib/_bootstrap_external.py
index 124948ef4..c1ceac96c 100644
--- a/vm/Lib/_bootstrap_external.py
+++ b/vm/Lib/_bootstrap_external.py
@@ -26,6 +26,16 @@ _CASE_INSENSITIVE_PLATFORMS =  (_CASE_INSENSITIVE_PLATFORMS_BYTES_KEY
                                 + _CASE_INSENSITIVE_PLATFORMS_STR_KEY)
 
 
+def _w_long(x):
+    """Convert a 32-bit integer to little-endian."""
+    return (int(x) & 0xFFFFFFFF).to_bytes(4, 'little')
+
+
+def _r_long(int_bytes):
+    """Convert 4 bytes in little-endian to an integer."""
+    return int.from_bytes(int_bytes, 'little')
+
+
 def _make_relax_case():
     if sys.platform.startswith(_CASE_INSENSITIVE_PLATFORMS):
         if sys.platform.startswith(_CASE_INSENSITIVE_PLATFORMS_STR_KEY):
diff --git a/vm/src/builtins.rs b/vm/src/builtins.rs
index e33ed2475..33ad00044 100644
--- a/vm/src/builtins.rs
+++ b/vm/src/builtins.rs
@@ -21,7 +21,6 @@ use crate::obj::objtype::{self, PyClassRef};
 #[cfg(feature = "rustpython-compiler")]
 use rustpython_compiler::compile;
 
-use crate::eval::get_compile_mode;
 use crate::function::{single_or_tuple_any, Args, KwArgs, OptionalArg, PyFuncArgs};
 use crate::pyobject::{
     Either, IdProtocol, IntoPyObject, ItemProtocol, PyIterable, PyObjectRef, PyResult, PyValue,
@@ -38,7 +37,7 @@ fn builtin_abs(x: PyObjectRef, vm: &VirtualMachine) -> PyResult {
     let method = vm.get_method_or_type_error(x.clone(), "__abs__", || {
         format!("bad operand type for abs(): '{}'", x.class().name)
     })?;
-    vm.invoke(method, PyFuncArgs::new(vec![], vec![]))
+    vm.invoke(&method, PyFuncArgs::new(vec![], vec![]))
 }
 
 fn builtin_all(iterable: PyIterable<bool>, vm: &VirtualMachine) -> PyResult<bool> {
@@ -125,9 +124,13 @@ fn builtin_compile(args: CompileArgs, vm: &VirtualMachine) -> PyResult<PyCodeRef
         Either::B(bytes) => str::from_utf8(&bytes).unwrap().to_string(),
     };
 
-    let mode = get_compile_mode(vm, &args.mode.value)?;
+    let mode = args
+        .mode
+        .as_str()
+        .parse::<compile::Mode>()
+        .map_err(|err| vm.new_value_error(err.to_string()))?;
 
-    vm.compile(&source, &mode, args.filename.value.to_string())
+    vm.compile(&source, mode, args.filename.value.to_string())
         .map_err(|err| vm.new_syntax_error(&err))
 }
 
@@ -175,7 +178,7 @@ fn builtin_eval(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
     } else if objtype::isinstance(source, &vm.ctx.str_type()) {
         let mode = compile::Mode::Eval;
         let source = objstr::get_value(source);
-        vm.compile(&source, &mode, "<string>".to_string())
+        vm.compile(&source, mode, "<string>".to_string())
             .map_err(|err| vm.new_syntax_error(&err))?
     } else {
         return Err(vm.new_type_error("code argument must be str or code object".to_string()));
@@ -202,7 +205,7 @@ fn builtin_exec(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
     let code_obj = if objtype::isinstance(source, &vm.ctx.str_type()) {
         let mode = compile::Mode::Exec;
         let source = objstr::get_value(source);
-        vm.compile(&source, &mode, "<string>".to_string())
+        vm.compile(&source, mode, "<string>".to_string())
             .map_err(|err| vm.new_syntax_error(&err))?
     } else if let Ok(code_obj) = PyCodeRef::try_from_object(vm, source.clone()) {
         code_obj
@@ -392,7 +395,7 @@ fn builtin_len(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
     let method = vm.get_method_or_type_error(obj.clone(), "__len__", || {
         format!("object of type '{}' has no len()", obj.class().name)
     })?;
-    vm.invoke(method, PyFuncArgs::default())
+    vm.invoke(&method, PyFuncArgs::default())
 }
 
 fn builtin_locals(vm: &VirtualMachine) -> PyDictRef {
@@ -425,15 +428,15 @@ fn builtin_max(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
     let mut x = candidates_iter.next().unwrap();
     // TODO: this key function looks pretty duplicate. Maybe we can create
     // a local function?
-    let mut x_key = if let Some(f) = &key_func {
-        vm.invoke(f.clone(), vec![x.clone()])?
+    let mut x_key = if let Some(ref f) = &key_func {
+        vm.invoke(f, vec![x.clone()])?
     } else {
         x.clone()
     };
 
     for y in candidates_iter {
-        let y_key = if let Some(f) = &key_func {
-            vm.invoke(f.clone(), vec![y.clone()])?
+        let y_key = if let Some(ref f) = &key_func {
+            vm.invoke(f, vec![y.clone()])?
         } else {
             y.clone()
         };
@@ -473,15 +476,15 @@ fn builtin_min(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
     let mut x = candidates_iter.next().unwrap();
     // TODO: this key function looks pretty duplicate. Maybe we can create
     // a local function?
-    let mut x_key = if let Some(f) = &key_func {
-        vm.invoke(f.clone(), vec![x.clone()])?
+    let mut x_key = if let Some(ref f) = &key_func {
+        vm.invoke(f, vec![x.clone()])?
     } else {
         x.clone()
     };
 
     for y in candidates_iter {
-        let y_key = if let Some(f) = &key_func {
-            vm.invoke(f.clone(), vec![y.clone()])?
+        let y_key = if let Some(ref f) = &key_func {
+            vm.invoke(f, vec![y.clone()])?
         } else {
             y.clone()
         };
@@ -708,7 +711,7 @@ fn builtin_reversed(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
     arg_check!(vm, args, required = [(obj, None)]);
 
     if let Some(reversed_method) = vm.get_method(obj.clone(), "__reversed__") {
-        vm.invoke(reversed_method?, PyFuncArgs::default())
+        vm.invoke(&reversed_method?, PyFuncArgs::default())
     } else {
         vm.get_method_or_type_error(obj.clone(), "__getitem__", || {
             "argument to reversed() must be a sequence".to_string()
@@ -731,9 +734,19 @@ fn builtin_round(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
         optional = [(ndigits, None)]
     );
     if let Some(ndigits) = ndigits {
-        let ndigits = vm.call_method(ndigits, "__int__", vec![])?;
-        let rounded = vm.call_method(number, "__round__", vec![ndigits])?;
-        Ok(rounded)
+        if objtype::isinstance(ndigits, &vm.ctx.int_type()) {
+            let ndigits = vm.call_method(ndigits, "__int__", vec![])?;
+            let rounded = vm.call_method(number, "__round__", vec![ndigits])?;
+            Ok(rounded)
+        } else if vm.ctx.none().is(ndigits) {
+            let rounded = &vm.call_method(number, "__round__", vec![])?;
+            Ok(vm.ctx.new_int(objint::get_value(rounded).clone()))
+        } else {
+            Err(vm.new_type_error(format!(
+                "'{}' object cannot be interpreted as an integer",
+                ndigits.class().name
+            )))
+        }
     } else {
         // without a parameter, the result type is coerced to int
         let rounded = &vm.call_method(number, "__round__", vec![])?;
@@ -774,7 +787,7 @@ fn builtin_sum(iterable: PyIterable, start: OptionalArg, vm: &VirtualMachine) ->
 
 // Should be renamed to builtin___import__?
 fn builtin_import(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
-    vm.invoke(vm.import_func.borrow().clone(), args)
+    vm.invoke(&vm.import_func.borrow(), args)
 }
 
 fn builtin_vars(obj: OptionalArg, vm: &VirtualMachine) -> PyResult {
@@ -949,7 +962,11 @@ pub fn builtin_build_class_(
         if objtype::issubclass(&base.class(), &metaclass) {
             metaclass = base.class();
         } else if !objtype::issubclass(&metaclass, &base.class()) {
-            return Err(vm.new_type_error("metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases".to_string()));
+            return Err(vm.new_type_error(
+                "metaclass conflict: the metaclass of a derived class must be a (non-strict) \
+                 subclass of the metaclasses of all its bases"
+                    .to_owned(),
+            ));
         }
     }
 
@@ -957,13 +974,13 @@ pub fn builtin_build_class_(
 
     // Prepare uses full __getattribute__ resolution chain.
     let prepare = vm.get_attribute(metaclass.clone().into_object(), "__prepare__")?;
-    let namespace = vm.invoke(prepare, vec![name_obj.clone(), bases.clone()])?;
+    let namespace = vm.invoke(&prepare, vec![name_obj.clone(), bases.clone()])?;
 
     let namespace: PyDictRef = TryFromObject::try_from_object(vm, namespace)?;
 
     let cells = vm.ctx.new_dict();
 
-    vm.invoke_with_locals(function, cells.clone(), namespace.clone())?;
+    vm.invoke_with_locals(&function, cells.clone(), namespace.clone())?;
 
     namespace.set_item("__name__", name_obj.clone(), vm)?;
     namespace.set_item("__qualname__", qualified_name.into_object(), vm)?;
diff --git a/vm/src/cformat.rs b/vm/src/cformat.rs
index 2b17b992a..cac22a3a5 100644
--- a/vm/src/cformat.rs
+++ b/vm/src/cformat.rs
@@ -209,6 +209,44 @@ impl CFormatSpec {
             self.fill_string(format!("{}{}", prefix, magnitude_string), ' ', None)
         }
     }
+
+    pub fn format_float(&self, num: f64) -> String {
+        let magnitude = num.abs();
+
+        let sign_string = if num.is_sign_positive() {
+            if self.flags.contains(CConversionFlags::SIGN_CHAR) {
+                "+"
+            } else if self.flags.contains(CConversionFlags::BLANK_SIGN) {
+                " "
+            } else {
+                ""
+            }
+        } else {
+            "-"
+        };
+
+        // TODO: Support precision
+        let magnitude_string = format!("{:.6}", magnitude);
+
+        if self.flags.contains(CConversionFlags::ZERO_PAD) {
+            let fill_char = if !self.flags.contains(CConversionFlags::LEFT_ADJUST) {
+                '0'
+            } else {
+                ' '
+            };
+            format!(
+                "{}{}",
+                sign_string,
+                self.fill_string(
+                    magnitude_string,
+                    fill_char,
+                    Some(sign_string.chars().count())
+                )
+            )
+        } else {
+            self.fill_string(format!("{}{}", sign_string, magnitude_string), ' ', None)
+        }
+    }
 }
 
 #[derive(Debug, PartialEq)]
@@ -763,6 +801,42 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_parse_and_format_float() {
+        assert_eq!(
+            "%f".parse::<CFormatSpec>()
+                .unwrap()
+                .format_float(f64::from(1.2345)),
+            "1.234500".to_string()
+        );
+        assert_eq!(
+            "%+f"
+                .parse::<CFormatSpec>()
+                .unwrap()
+                .format_float(f64::from(1.2345)),
+            "+1.234500".to_string()
+        );
+        assert_eq!(
+            "% f"
+                .parse::<CFormatSpec>()
+                .unwrap()
+                .format_float(f64::from(1.2345)),
+            " 1.234500".to_string()
+        );
+        assert_eq!(
+            "%f".parse::<CFormatSpec>()
+                .unwrap()
+                .format_float(f64::from(-1.2345)),
+            "-1.234500".to_string()
+        );
+        assert_eq!(
+            "%f".parse::<CFormatSpec>()
+                .unwrap()
+                .format_float(f64::from(1.2345678901)),
+            "1.234568".to_string()
+        );
+    }
+
     #[test]
     fn test_format_parse() {
         let fmt = "Hello, my name is %s and I'm %d years old";
diff --git a/vm/src/eval.rs b/vm/src/eval.rs
index 48106cd5c..8feeb8741 100644
--- a/vm/src/eval.rs
+++ b/vm/src/eval.rs
@@ -4,7 +4,7 @@ use crate::vm::VirtualMachine;
 use rustpython_compiler::compile;
 
 pub fn eval(vm: &VirtualMachine, source: &str, scope: Scope, source_path: &str) -> PyResult {
-    match vm.compile(source, &compile::Mode::Eval, source_path.to_string()) {
+    match vm.compile(source, compile::Mode::Eval, source_path.to_string()) {
         Ok(bytecode) => {
             debug!("Code object: {:?}", bytecode);
             vm.run_code_obj(bytecode, scope)
@@ -13,17 +13,6 @@ pub fn eval(vm: &VirtualMachine, source: &str, scope: Scope, source_path: &str)
     }
 }
 
-pub fn get_compile_mode(vm: &VirtualMachine, mode: &str) -> PyResult<compile::Mode> {
-    match mode {
-        "exec" => Ok(compile::Mode::Exec),
-        "eval" => Ok(compile::Mode::Eval),
-        "single" => Ok(compile::Mode::Single),
-        _ => {
-            Err(vm.new_value_error("compile() mode must be 'exec', 'eval' or 'single'".to_string()))
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::eval;
diff --git a/vm/src/exceptions.rs b/vm/src/exceptions.rs
index 48fa0ce7a..a78a286b8 100644
--- a/vm/src/exceptions.rs
+++ b/vm/src/exceptions.rs
@@ -3,7 +3,8 @@ use crate::obj::objsequence;
 use crate::obj::objtuple::{PyTuple, PyTupleRef};
 use crate::obj::objtype;
 use crate::obj::objtype::PyClassRef;
-use crate::pyobject::{create_type, IdProtocol, PyContext, PyObjectRef, PyResult, TypeProtocol};
+use crate::pyobject::{IdProtocol, PyContext, PyObjectRef, PyResult, TypeProtocol};
+use crate::types::create_type;
 use crate::vm::VirtualMachine;
 use itertools::Itertools;
 use std::fs::File;
diff --git a/vm/src/frame.rs b/vm/src/frame.rs
index 4cbb022a5..0f56596ee 100644
--- a/vm/src/frame.rs
+++ b/vm/src/frame.rs
@@ -198,10 +198,7 @@ impl Frame {
                 ref symbols,
                 ref level,
             } => self.import(vm, name, symbols, *level),
-            bytecode::Instruction::ImportStar {
-                ref name,
-                ref level,
-            } => self.import_star(vm, name, *level),
+            bytecode::Instruction::ImportStar => self.import_star(vm),
             bytecode::Instruction::ImportFrom { ref name } => self.import_from(vm, name),
             bytecode::Instruction::LoadName {
                 ref name,
@@ -488,7 +485,7 @@ impl Frame {
 
                 // Call function:
                 let func_ref = self.pop_value();
-                let value = vm.invoke(func_ref, args)?;
+                let value = vm.invoke(&func_ref, args)?;
                 self.push_value(value);
                 Ok(None)
             }
@@ -496,7 +493,7 @@ impl Frame {
                 self.jump(*target);
                 Ok(None)
             }
-            bytecode::Instruction::JumpIf { target } => {
+            bytecode::Instruction::JumpIfTrue { target } => {
                 let obj = self.pop_value();
                 let value = objbool::boolval(vm, obj)?;
                 if value {
@@ -514,6 +511,28 @@ impl Frame {
                 Ok(None)
             }
 
+            bytecode::Instruction::JumpIfTrueOrPop { target } => {
+                let obj = self.last_value();
+                let value = objbool::boolval(vm, obj)?;
+                if value {
+                    self.jump(*target);
+                } else {
+                    self.pop_value();
+                }
+                Ok(None)
+            }
+
+            bytecode::Instruction::JumpIfFalseOrPop { target } => {
+                let obj = self.last_value();
+                let value = objbool::boolval(vm, obj)?;
+                if !value {
+                    self.jump(*target);
+                } else {
+                    self.pop_value();
+                }
+                Ok(None)
+            }
+
             bytecode::Instruction::Raise { argc } => {
                 let cause = match argc {
                     2 => self.get_exception(vm, true)?,
@@ -577,7 +596,7 @@ impl Frame {
                 if !expr.is(&vm.get_none()) {
                     let repr = vm.to_repr(&expr)?;
                     // TODO: implement sys.displayhook
-                    if let Ok(print) = vm.get_attribute(vm.builtins.clone(), "print") {
+                    if let Ok(ref print) = vm.get_attribute(vm.builtins.clone(), "print") {
                         vm.invoke(print, vec![repr.into_object()])?;
                     }
                 }
@@ -718,25 +737,23 @@ impl Frame {
         // Load attribute, and transform any error into import error.
         let obj = vm
             .get_attribute(module, name)
-            .map_err(|_| vm.new_import_error(format!("cannot import name '{}'", name)));
-        self.push_value(obj?);
+            .map_err(|_| vm.new_import_error(format!("cannot import name '{}'", name)))?;
+        self.push_value(obj);
         Ok(None)
     }
 
     #[cfg_attr(feature = "flame-it", flame("Frame"))]
-    fn import_star(
-        &self,
-        vm: &VirtualMachine,
-        module: &Option<String>,
-        level: usize,
-    ) -> FrameResult {
-        let module = module.clone().unwrap_or_default();
-        let module = vm.import(&module, &vm.ctx.new_tuple(vec![]), level)?;
+    fn import_star(&self, vm: &VirtualMachine) -> FrameResult {
+        let module = self.pop_value();
 
         // Grab all the names from the module and put them in the context
         if let Some(dict) = &module.dict {
             for (k, v) in dict {
-                self.scope.store_name(&vm, &objstr::get_value(&k), v);
+                let k = vm.to_str(&k)?;
+                let k = k.as_str();
+                if !k.starts_with('_') {
+                    self.scope.store_name(&vm, k, v);
+                }
             }
         }
         Ok(None)
diff --git a/vm/src/function.rs b/vm/src/function.rs
index d199860b1..9874309fc 100644
--- a/vm/src/function.rs
+++ b/vm/src/function.rs
@@ -393,6 +393,18 @@ impl<T> OptionalArg<T> {
     }
 }
 
+pub type OptionalOption<T> = OptionalArg<Option<T>>;
+
+impl<T> OptionalOption<T> {
+    #[inline]
+    pub fn flat_option(self) -> Option<T> {
+        match self {
+            Present(Some(value)) => Some(value),
+            _ => None,
+        }
+    }
+}
+
 impl<T> FromArgs for OptionalArg<T>
 where
     T: TryFromObject,
diff --git a/vm/src/import.rs b/vm/src/import.rs
index d48d36466..267adfc86 100644
--- a/vm/src/import.rs
+++ b/vm/src/import.rs
@@ -17,14 +17,14 @@ pub fn init_importlib(vm: &VirtualMachine, external: bool) -> PyResult {
     let importlib = import_frozen(vm, "_frozen_importlib")?;
     let impmod = import_builtin(vm, "_imp")?;
     let install = vm.get_attribute(importlib.clone(), "_install")?;
-    vm.invoke(install, vec![vm.sys_module.clone(), impmod])?;
+    vm.invoke(&install, vec![vm.sys_module.clone(), impmod])?;
     vm.import_func
         .replace(vm.get_attribute(importlib.clone(), "__import__")?);
     if external && cfg!(feature = "rustpython-compiler") {
         flame_guard!("install_external");
         let install_external =
             vm.get_attribute(importlib.clone(), "_install_external_importers")?;
-        vm.invoke(install_external, vec![])?;
+        vm.invoke(&install_external, vec![])?;
         // Set pyc magic number to commit hash. Should be changed when bytecode will be more stable.
         let importlib_external =
             vm.import("_frozen_importlib_external", &vm.ctx.new_tuple(vec![]), 0)?;
@@ -68,7 +68,7 @@ pub fn import_file(
 ) -> PyResult {
     let code_obj = compile::compile(
         &content,
-        &compile::Mode::Exec,
+        compile::Mode::Exec,
         file_path,
         vm.settings.optimize,
     )
@@ -87,7 +87,7 @@ pub fn import_codeobj(
     if set_file_attr {
         attrs.set_item("__file__", vm.new_str(code_obj.source_path.to_owned()), vm)?;
     }
-    let module = vm.ctx.new_module(module_name, attrs.clone());
+    let module = vm.new_module(module_name, attrs.clone());
 
     // Store module in cache to prevent infinite loop with mutual importing libs:
     let sys_modules = vm.get_attribute(vm.sys_module.clone(), "modules")?;
diff --git a/vm/src/lib.rs b/vm/src/lib.rs
index 766ece06f..0f66f7f8b 100644
--- a/vm/src/lib.rs
+++ b/vm/src/lib.rs
@@ -68,6 +68,7 @@ pub mod scope;
 pub mod stdlib;
 mod sysmodule;
 mod traceback;
+pub mod types;
 pub mod util;
 mod version;
 mod vm;
diff --git a/vm/src/macros.rs b/vm/src/macros.rs
index 5ae975d8e..ea10abfdc 100644
--- a/vm/src/macros.rs
+++ b/vm/src/macros.rs
@@ -117,7 +117,7 @@ macro_rules! no_kwargs {
 #[macro_export]
 macro_rules! py_module {
     ( $vm:expr, $module_name:expr, { $($name:expr => $value:expr),* $(,)* }) => {{
-        let module = $vm.ctx.new_module($module_name, $vm.ctx.new_dict());
+        let module = $vm.new_module($module_name, $vm.ctx.new_dict());
         $vm.set_attr(&module, "__name__", $vm.ctx.new_str($module_name.to_string())).unwrap();
         $(
             $vm.set_attr(&module, $name, $value).unwrap();
diff --git a/vm/src/obj/objbool.rs b/vm/src/obj/objbool.rs
index 6988028ea..19d95889f 100644
--- a/vm/src/obj/objbool.rs
+++ b/vm/src/obj/objbool.rs
@@ -28,7 +28,7 @@ pub fn boolval(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<bool> {
         Some(method_or_err) => {
             // If descriptor returns Error, propagate it further
             let method = method_or_err?;
-            let bool_obj = vm.invoke(method, PyFuncArgs::default())?;
+            let bool_obj = vm.invoke(&method, PyFuncArgs::default())?;
             match bool_obj.payload::<PyInt>() {
                 Some(int_obj) => !int_obj.as_bigint().is_zero(),
                 None => {
@@ -42,7 +42,7 @@ pub fn boolval(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<bool> {
         None => match vm.get_method(obj.clone(), "__len__") {
             Some(method_or_err) => {
                 let method = method_or_err?;
-                let bool_obj = vm.invoke(method, PyFuncArgs::default())?;
+                let bool_obj = vm.invoke(&method, PyFuncArgs::default())?;
                 match bool_obj.payload::<PyInt>() {
                     Some(int_obj) => !int_obj.as_bigint().is_zero(),
                     None => {
@@ -66,7 +66,7 @@ Returns True when the argument x is true, False otherwise.
 The builtins True and False are the only two instances of the class bool.
 The class bool is a subclass of the class int, and cannot be subclassed.";
 
-    let bool_type = &context.bool_type;
+    let bool_type = &context.types.bool_type;
     extend_class!(context, bool_type, {
         "__new__" => context.new_rustfunc(bool_new),
         "__repr__" => context.new_rustfunc(bool_repr),
diff --git a/vm/src/obj/objbytearray.rs b/vm/src/obj/objbytearray.rs
index 51d608b09..c3d722ea7 100644
--- a/vm/src/obj/objbytearray.rs
+++ b/vm/src/obj/objbytearray.rs
@@ -78,14 +78,14 @@ impl PyValue for PyByteArray {
 
 /// Fill bytearray class methods dictionary.
 pub fn init(context: &PyContext) {
-    PyByteArrayRef::extend_class(context, &context.bytearray_type);
-    let bytearray_type = &context.bytearray_type;
+    PyByteArrayRef::extend_class(context, &context.types.bytearray_type);
+    let bytearray_type = &context.types.bytearray_type;
     extend_class!(context, bytearray_type, {
     "fromhex" => context.new_rustfunc(PyByteArrayRef::fromhex),
     "maketrans" => context.new_rustfunc(PyByteInner::maketrans),
     });
 
-    PyByteArrayIterator::extend_class(context, &context.bytearrayiterator_type);
+    PyByteArrayIterator::extend_class(context, &context.types.bytearrayiterator_type);
 }
 
 #[pyimpl]
diff --git a/vm/src/obj/objbytes.rs b/vm/src/obj/objbytes.rs
index 8e3149b17..c39b3203d 100644
--- a/vm/src/obj/objbytes.rs
+++ b/vm/src/obj/objbytes.rs
@@ -11,7 +11,8 @@ use std::ops::Deref;
 
 use crate::function::OptionalArg;
 use crate::pyobject::{
-    PyClassImpl, PyContext, PyIterable, PyObjectRef, PyRef, PyResult, PyValue, TryFromObject,
+    IntoPyObject, PyClassImpl, PyContext, PyIterable, PyObjectRef, PyRef, PyResult, PyValue,
+    TryFromObject,
 };
 
 use super::objbyteinner::{
@@ -59,6 +60,12 @@ impl PyBytes {
     }
 }
 
+impl IntoPyObject for Vec<u8> {
+    fn into_pyobject(self, vm: &VirtualMachine) -> PyResult {
+        Ok(vm.ctx.new_bytes(self))
+    }
+}
+
 impl Deref for PyBytes {
     type Target = [u8];
 
@@ -78,14 +85,14 @@ pub fn get_value<'a>(obj: &'a PyObjectRef) -> impl Deref<Target = Vec<u8>> + 'a
 }
 
 pub fn init(context: &PyContext) {
-    PyBytesRef::extend_class(context, &context.bytes_type);
-    let bytes_type = &context.bytes_type;
+    PyBytesRef::extend_class(context, &context.types.bytes_type);
+    let bytes_type = &context.types.bytes_type;
     extend_class!(context, bytes_type, {
     "fromhex" => context.new_rustfunc(PyBytesRef::fromhex),
     "maketrans" => context.new_rustfunc(PyByteInner::maketrans),
 
     });
-    PyBytesIterator::extend_class(context, &context.bytesiterator_type);
+    PyBytesIterator::extend_class(context, &context.types.bytesiterator_type);
 }
 
 #[pyimpl]
diff --git a/vm/src/obj/objclassmethod.rs b/vm/src/obj/objclassmethod.rs
index 10b3106ec..38ef47d9e 100644
--- a/vm/src/obj/objclassmethod.rs
+++ b/vm/src/obj/objclassmethod.rs
@@ -65,5 +65,5 @@ impl PyClassMethod {
 }
 
 pub fn init(context: &PyContext) {
-    PyClassMethod::extend_class(context, &context.classmethod_type);
+    PyClassMethod::extend_class(context, &context.types.classmethod_type);
 }
diff --git a/vm/src/obj/objcode.rs b/vm/src/obj/objcode.rs
index 51a73d614..a1671d0ef 100644
--- a/vm/src/obj/objcode.rs
+++ b/vm/src/obj/objcode.rs
@@ -81,7 +81,7 @@ impl PyCodeRef {
 }
 
 pub fn init(context: &PyContext) {
-    extend_class!(context, &context.code_type, {
+    extend_class!(context, &context.types.code_type, {
         "__new__" => context.new_rustfunc(PyCodeRef::new),
         "__repr__" => context.new_rustfunc(PyCodeRef::repr),
 
diff --git a/vm/src/obj/objcomplex.rs b/vm/src/obj/objcomplex.rs
index b32fd8f74..c20431d00 100644
--- a/vm/src/obj/objcomplex.rs
+++ b/vm/src/obj/objcomplex.rs
@@ -41,7 +41,7 @@ impl From<Complex64> for PyComplex {
 }
 
 pub fn init(context: &PyContext) {
-    PyComplex::extend_class(context, &context.complex_type);
+    PyComplex::extend_class(context, &context.types.complex_type);
 }
 
 pub fn get_value(obj: &PyObjectRef) -> Complex64 {
@@ -258,4 +258,12 @@ impl PyComplex {
         let ret = Wrapping(re_hash) + Wrapping(im_hash) * Wrapping(pyhash::IMAG);
         ret.0
     }
+
+    #[pymethod(name = "__getnewargs__")]
+    fn complex_getnewargs(&self, vm: &VirtualMachine) -> PyResult {
+        let Complex64 { re, im } = self.value;
+        Ok(vm
+            .ctx
+            .new_tuple(vec![vm.ctx.new_float(re), vm.ctx.new_float(im)]))
+    }
 }
diff --git a/vm/src/obj/objdict.rs b/vm/src/obj/objdict.rs
index e68c6b6a4..09fc08a96 100644
--- a/vm/src/obj/objdict.rs
+++ b/vm/src/obj/objdict.rs
@@ -210,7 +210,7 @@ impl PyDictRef {
         }
         if let Some(method_or_err) = vm.get_method(self.clone().into_object(), "__missing__") {
             let method = method_or_err?;
-            return vm.invoke(method, vec![key]);
+            return vm.invoke(&method, vec![key]);
         }
         Err(vm.new_key_error(key.clone()))
     }
@@ -423,7 +423,7 @@ macro_rules! dict_iterator {
 
         impl PyValue for $name {
             fn class(vm: &VirtualMachine) -> PyClassRef {
-                vm.ctx.$class.clone()
+                vm.ctx.types.$class.clone()
             }
         }
 
@@ -473,7 +473,7 @@ macro_rules! dict_iterator {
 
         impl PyValue for $iter_name {
             fn class(vm: &VirtualMachine) -> PyClassRef {
-                vm.ctx.$iter_class.clone()
+                vm.ctx.types.$iter_class.clone()
             }
         }
     };
@@ -511,7 +511,7 @@ dict_iterator! {
 }
 
 pub fn init(context: &PyContext) {
-    extend_class!(context, &context.dict_type, {
+    extend_class!(context, &context.types.dict_type, {
         "__bool__" => context.new_rustfunc(PyDictRef::bool),
         "__len__" => context.new_rustfunc(PyDictRef::len),
         "__contains__" => context.new_rustfunc(PyDictRef::contains),
@@ -536,10 +536,10 @@ pub fn init(context: &PyContext) {
         "popitem" => context.new_rustfunc(PyDictRef::popitem),
     });
 
-    PyDictKeys::extend_class(context, &context.dictkeys_type);
-    PyDictKeyIterator::extend_class(context, &context.dictkeyiterator_type);
-    PyDictValues::extend_class(context, &context.dictvalues_type);
-    PyDictValueIterator::extend_class(context, &context.dictvalueiterator_type);
-    PyDictItems::extend_class(context, &context.dictitems_type);
-    PyDictItemIterator::extend_class(context, &context.dictitemiterator_type);
+    PyDictKeys::extend_class(context, &context.types.dictkeys_type);
+    PyDictKeyIterator::extend_class(context, &context.types.dictkeyiterator_type);
+    PyDictValues::extend_class(context, &context.types.dictvalues_type);
+    PyDictValueIterator::extend_class(context, &context.types.dictvalueiterator_type);
+    PyDictItems::extend_class(context, &context.types.dictitems_type);
+    PyDictItemIterator::extend_class(context, &context.types.dictitemiterator_type);
 }
diff --git a/vm/src/obj/objellipsis.rs b/vm/src/obj/objellipsis.rs
index cb188e1f1..3b2b6d8bf 100644
--- a/vm/src/obj/objellipsis.rs
+++ b/vm/src/obj/objellipsis.rs
@@ -1,20 +1,30 @@
-use crate::function::PyFuncArgs;
-use crate::pyobject::{PyContext, PyResult};
+use crate::obj::objtype::{issubclass, PyClassRef};
+use crate::pyobject::{PyContext, PyEllipsisRef, PyResult};
 use crate::vm::VirtualMachine;
 
 pub fn init(context: &PyContext) {
     extend_class!(context, &context.ellipsis_type, {
         "__new__" => context.new_rustfunc(ellipsis_new),
-        "__repr__" => context.new_rustfunc(ellipsis_repr)
+        "__repr__" => context.new_rustfunc(ellipsis_repr),
+        "__reduce__" => context.new_rustfunc(ellipsis_reduce),
     });
 }
 
-fn ellipsis_new(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
-    arg_check!(vm, args, required = [(_cls, None)]);
-    Ok(vm.ctx.ellipsis())
+fn ellipsis_new(cls: PyClassRef, vm: &VirtualMachine) -> PyResult {
+    if issubclass(&cls, &vm.ctx.ellipsis_type) {
+        Ok(vm.ctx.ellipsis())
+    } else {
+        Err(vm.new_type_error(format!(
+            "ellipsis.__new__({ty}): {ty} is not a subtype of ellipsis",
+            ty = cls,
+        )))
+    }
 }
 
-fn ellipsis_repr(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
-    arg_check!(vm, args, required = [(_cls, None)]);
-    Ok(vm.new_str("Ellipsis".to_string()))
+fn ellipsis_repr(_self: PyEllipsisRef, _vm: &VirtualMachine) -> String {
+    "Ellipsis".to_string()
+}
+
+fn ellipsis_reduce(_self: PyEllipsisRef, _vm: &VirtualMachine) -> String {
+    "Ellipsis".to_string()
 }
diff --git a/vm/src/obj/objenumerate.rs b/vm/src/obj/objenumerate.rs
index 56d232272..0ce34c689 100644
--- a/vm/src/obj/objenumerate.rs
+++ b/vm/src/obj/objenumerate.rs
@@ -68,8 +68,8 @@ impl PyEnumerate {
 }
 
 pub fn init(context: &PyContext) {
-    PyEnumerate::extend_class(context, &context.enumerate_type);
-    extend_class!(context, &context.enumerate_type, {
+    PyEnumerate::extend_class(context, &context.types.enumerate_type);
+    extend_class!(context, &context.types.enumerate_type, {
         "__new__" => context.new_rustfunc(enumerate_new),
     });
 }
diff --git a/vm/src/obj/objfilter.rs b/vm/src/obj/objfilter.rs
index 24800d6aa..8fa3fef3c 100644
--- a/vm/src/obj/objfilter.rs
+++ b/vm/src/obj/objfilter.rs
@@ -52,7 +52,7 @@ impl PyFilter {
             } else {
                 // the predicate itself can raise StopIteration which does stop the filter
                 // iteration
-                vm.invoke(predicate.clone(), vec![next_obj.clone()])?
+                vm.invoke(&predicate, vec![next_obj.clone()])?
             };
             if objbool::boolval(vm, predicate_value)? {
                 return Ok(next_obj);
@@ -67,8 +67,8 @@ impl PyFilter {
 }
 
 pub fn init(context: &PyContext) {
-    PyFilter::extend_class(context, &context.filter_type);
-    extend_class!(context, &context.filter_type, {
+    PyFilter::extend_class(context, &context.types.filter_type);
+    extend_class!(context, &context.types.filter_type, {
         "__new__" => context.new_rustfunc(filter_new),
     });
 }
diff --git a/vm/src/obj/objfloat.rs b/vm/src/obj/objfloat.rs
index cfac52aa9..b0dbaebe2 100644
--- a/vm/src/obj/objfloat.rs
+++ b/vm/src/obj/objfloat.rs
@@ -440,25 +440,38 @@ impl PyFloat {
             OptionalArg::Missing => None,
             OptionalArg::Present(ref value) => {
                 if !vm.get_none().is(value) {
-                    let ndigits = if objtype::isinstance(value, &vm.ctx.int_type()) {
-                        objint::get_value(value)
-                    } else {
+                    if !objtype::isinstance(value, &vm.ctx.int_type()) {
                         return Err(vm.new_type_error(format!(
-                            "TypeError: '{}' object cannot be interpreted as an integer",
+                            "'{}' object cannot be interpreted as an integer",
                             value.class().name
                         )));
                     };
-                    if ndigits.is_zero() {
-                        None
-                    } else {
-                        Some(ndigits)
-                    }
+                    // Only accept int type ndigits
+                    let ndigits = objint::get_value(value);
+                    Some(ndigits)
                 } else {
                     None
                 }
             }
         };
-        if ndigits.is_none() {
+
+        if let Some(ndigits) = ndigits {
+            if ndigits.is_zero() {
+                let fract = self.value.fract();
+                let value = if (fract.abs() - 0.5).abs() < std::f64::EPSILON {
+                    if self.value.trunc() % 2.0 == 0.0 {
+                        self.value - fract
+                    } else {
+                        self.value + fract
+                    }
+                } else {
+                    self.value.round()
+                };
+                Ok(vm.ctx.new_float(value))
+            } else {
+                Ok(vm.ctx.not_implemented())
+            }
+        } else {
             let fract = self.value.fract();
             let value = if (fract.abs() - 0.5).abs() < std::f64::EPSILON {
                 if self.value.trunc() % 2.0 == 0.0 {
@@ -471,8 +484,6 @@ impl PyFloat {
             };
             let int = try_to_bigint(value, vm)?;
             Ok(vm.ctx.new_int(int))
-        } else {
-            Ok(vm.ctx.not_implemented())
         }
     }
 
@@ -612,12 +623,12 @@ pub fn make_float(vm: &VirtualMachine, obj: &PyObjectRef) -> PyResult<f64> {
                 obj.class().name
             )
         })?;
-        let result = vm.invoke(method, vec![])?;
+        let result = vm.invoke(&method, vec![])?;
         Ok(get_value(&result))
     }
 }
 
 #[rustfmt::skip] // to avoid line splitting
 pub fn init(context: &PyContext) {
-    PyFloat::extend_class(context, &context.float_type);
+    PyFloat::extend_class(context, &context.types.float_type);
 }
diff --git a/vm/src/obj/objframe.rs b/vm/src/obj/objframe.rs
index 73f4e9b91..efc833270 100644
--- a/vm/src/obj/objframe.rs
+++ b/vm/src/obj/objframe.rs
@@ -9,7 +9,7 @@ use crate::pyobject::{PyContext, PyObjectRef, PyResult};
 use crate::vm::VirtualMachine;
 
 pub fn init(context: &PyContext) {
-    extend_class!(context, &context.frame_type, {
+    extend_class!(context, &context.types.frame_type, {
         "__new__" => context.new_rustfunc(FrameRef::new),
         "__repr__" => context.new_rustfunc(FrameRef::repr),
         "f_locals" => context.new_property(FrameRef::flocals),
diff --git a/vm/src/obj/objfunction.rs b/vm/src/obj/objfunction.rs
index 1c7ff642a..d33ec97fe 100644
--- a/vm/src/obj/objfunction.rs
+++ b/vm/src/obj/objfunction.rs
@@ -42,7 +42,7 @@ impl PyValue for PyFunction {
 
 impl PyFunctionRef {
     fn call(self, args: Args, kwargs: KwArgs, vm: &VirtualMachine) -> PyResult {
-        vm.invoke(self.into_object(), (&args, &kwargs))
+        vm.invoke(&self.into_object(), (&args, &kwargs))
     }
 
     fn code(self, _vm: &VirtualMachine) -> PyCodeRef {
@@ -78,7 +78,7 @@ impl PyValue for PyMethod {
 }
 
 pub fn init(context: &PyContext) {
-    let function_type = &context.function_type;
+    let function_type = &context.types.function_type;
     extend_class!(context, function_type, {
         "__get__" => context.new_rustfunc(bind_method),
         "__call__" => context.new_rustfunc(PyFunctionRef::call),
@@ -87,7 +87,7 @@ pub fn init(context: &PyContext) {
         "__kwdefaults__" => context.new_property(PyFunctionRef::kwdefaults),
     });
 
-    let builtin_function_or_method_type = &context.builtin_function_or_method_type;
+    let builtin_function_or_method_type = &context.types.builtin_function_or_method_type;
     extend_class!(context, builtin_function_or_method_type, {
         "__get__" => context.new_rustfunc(bind_method)
     });
diff --git a/vm/src/obj/objgenerator.rs b/vm/src/obj/objgenerator.rs
index 2c51778fd..a26be543d 100644
--- a/vm/src/obj/objgenerator.rs
+++ b/vm/src/obj/objgenerator.rs
@@ -75,5 +75,5 @@ fn handle_execution_result(result: ExecutionResult, vm: &VirtualMachine) -> PyRe
 }
 
 pub fn init(ctx: &PyContext) {
-    PyGenerator::extend_class(ctx, &ctx.generator_type);
+    PyGenerator::extend_class(ctx, &ctx.types.generator_type);
 }
diff --git a/vm/src/obj/objint.rs b/vm/src/obj/objint.rs
index a158eb344..cfe86f7bc 100644
--- a/vm/src/obj/objint.rs
+++ b/vm/src/obj/objint.rs
@@ -6,18 +6,19 @@ use num_traits::{One, Pow, Signed, ToPrimitive, Zero};
 
 use crate::format::FormatSpec;
 use crate::function::{KwArgs, OptionalArg, PyFuncArgs};
+use crate::obj::objtype::PyClassRef;
 use crate::pyhash;
 use crate::pyobject::{
-    IntoPyObject, PyClassImpl, PyContext, PyObjectRef, PyRef, PyResult, PyValue, TryFromObject,
-    TypeProtocol,
+    IdProtocol, IntoPyObject, PyClassImpl, PyContext, PyObjectRef, PyRef, PyResult, PyValue,
+    TryFromObject, TypeProtocol,
 };
 use crate::vm::VirtualMachine;
 
 use super::objbyteinner::PyByteInner;
 use super::objbytes::PyBytes;
+use super::objint;
 use super::objstr::{PyString, PyStringRef};
 use super::objtype;
-use crate::obj::objtype::PyClassRef;
 
 /// int(x=0) -> integer
 /// int(x, base=10) -> integer
@@ -139,13 +140,42 @@ fn inner_pow(int1: &PyInt, int2: &PyInt, vm: &VirtualMachine) -> PyResult {
 }
 
 fn inner_mod(int1: &PyInt, int2: &PyInt, vm: &VirtualMachine) -> PyResult {
-    if int2.value != BigInt::zero() {
-        Ok(vm.ctx.new_int(&int1.value % &int2.value))
-    } else {
+    if int2.value.is_zero() {
         Err(vm.new_zero_division_error("integer modulo by zero".to_string()))
+    } else {
+        Ok(vm.ctx.new_int(&int1.value % &int2.value))
     }
 }
 
+fn inner_floordiv(int1: &PyInt, int2: &PyInt, vm: &VirtualMachine) -> PyResult {
+    if int2.value.is_zero() {
+        Err(vm.new_zero_division_error("integer division by zero".to_string()))
+    } else {
+        Ok(vm.ctx.new_int(int1.value.div_floor(&int2.value)))
+    }
+}
+
+fn inner_divmod(int1: &PyInt, int2: &PyInt, vm: &VirtualMachine) -> PyResult {
+    if int2.value.is_zero() {
+        Err(vm.new_zero_division_error("integer division or modulo by zero".to_string()))
+    } else {
+        let (div, modulo) = int1.value.div_mod_floor(&int2.value);
+        Ok(vm
+            .ctx
+            .new_tuple(vec![vm.ctx.new_int(div), vm.ctx.new_int(modulo)]))
+    }
+}
+
+fn inner_lshift(int1: &PyInt, int2: &PyInt, vm: &VirtualMachine) -> PyResult {
+    let n_bits = get_shift_amount(int2, vm)?;
+    Ok(vm.ctx.new_int(&int1.value << n_bits))
+}
+
+fn inner_rshift(int1: &PyInt, int2: &PyInt, vm: &VirtualMachine) -> PyResult {
+    let n_bits = get_shift_amount(int2, vm)?;
+    Ok(vm.ctx.new_int(&int1.value >> n_bits))
+}
+
 #[pyimpl]
 impl PyInt {
     #[pymethod(name = "__eq__")]
@@ -269,13 +299,18 @@ impl PyInt {
     #[pymethod(name = "__floordiv__")]
     fn floordiv(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
         if objtype::isinstance(&other, &vm.ctx.int_type()) {
-            let v2 = get_value(&other);
-            if *v2 != BigInt::zero() {
-                let modulo = (&self.value % v2 + v2) % v2;
-                Ok(vm.ctx.new_int((&self.value - modulo) / v2))
-            } else {
-                Err(vm.new_zero_division_error("integer floordiv by zero".to_string()))
-            }
+            let other = get_py_int(&other);
+            inner_floordiv(self, &other, &vm)
+        } else {
+            Ok(vm.ctx.not_implemented())
+        }
+    }
+
+    #[pymethod(name = "__rfloordiv__")]
+    fn rfloordiv(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+        if objtype::isinstance(&other, &vm.ctx.int_type()) {
+            let other = get_py_int(&other);
+            inner_floordiv(&other, self, &vm)
         } else {
             Ok(vm.ctx.not_implemented())
         }
@@ -287,18 +322,18 @@ impl PyInt {
             return Ok(vm.ctx.not_implemented());
         }
 
-        if let Some(n_bits) = get_value(&other).to_usize() {
-            return Ok(vm.ctx.new_int((&self.value) << n_bits));
+        let other = get_py_int(&other);
+        inner_lshift(self, other, vm)
+    }
+
+    #[pymethod(name = "__rlshift__")]
+    fn rlshift(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+        if !objtype::isinstance(&other, &vm.ctx.int_type()) {
+            return Ok(vm.ctx.not_implemented());
         }
 
-        // i2 failed `to_usize()` conversion
-        match get_value(&other) {
-            v if *v < BigInt::zero() => Err(vm.new_value_error("negative shift count".to_string())),
-            v if *v > BigInt::from(usize::max_value()) => {
-                Err(vm.new_overflow_error("the number is too large to convert to int".to_string()))
-            }
-            _ => panic!("Failed converting {} to rust usize", get_value(&other)),
-        }
+        let other = get_py_int(&other);
+        inner_lshift(other, self, vm)
     }
 
     #[pymethod(name = "__rshift__")]
@@ -307,18 +342,18 @@ impl PyInt {
             return Ok(vm.ctx.not_implemented());
         }
 
-        if let Some(n_bits) = get_value(&other).to_usize() {
-            return Ok(vm.ctx.new_int((&self.value) >> n_bits));
+        let other = get_py_int(&other);
+        inner_rshift(self, other, vm)
+    }
+
+    #[pymethod(name = "__rrshift__")]
+    fn rrshift(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+        if !objtype::isinstance(&other, &vm.ctx.int_type()) {
+            return Ok(vm.ctx.not_implemented());
         }
 
-        // i2 failed `to_usize()` conversion
-        match get_value(&other) {
-            v if *v < BigInt::zero() => Err(vm.new_value_error("negative shift count".to_string())),
-            v if *v > BigInt::from(usize::max_value()) => {
-                Err(vm.new_overflow_error("the number is too large to convert to int".to_string()))
-            }
-            _ => panic!("Failed converting {} to rust usize", get_value(&other)),
-        }
+        let other = get_py_int(&other);
+        inner_rshift(other, self, vm)
     }
 
     #[pymethod(name = "__xor__")]
@@ -344,6 +379,11 @@ impl PyInt {
         }
     }
 
+    #[pymethod(name = "__ror__")]
+    fn ror(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyObjectRef {
+        self.or(other, vm)
+    }
+
     #[pymethod(name = "__and__")]
     pub fn and(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyObjectRef {
         if objtype::isinstance(&other, &vm.ctx.int_type()) {
@@ -354,10 +394,15 @@ impl PyInt {
         }
     }
 
+    #[pymethod(name = "__rand__")]
+    fn rand(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyObjectRef {
+        self.and(other, vm)
+    }
+
     #[pymethod(name = "__pow__")]
     fn pow(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
         if objtype::isinstance(&other, &vm.ctx.int_type()) {
-            let other = other.payload::<PyInt>().unwrap();
+            let other = get_py_int(&other);
             inner_pow(self, &other, vm)
         } else {
             Ok(vm.ctx.not_implemented())
@@ -367,7 +412,7 @@ impl PyInt {
     #[pymethod(name = "__rpow__")]
     fn rpow(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
         if objtype::isinstance(&other, &vm.ctx.int_type()) {
-            let other = other.payload::<PyInt>().unwrap();
+            let other = get_py_int(&other);
             inner_pow(&other, self, vm)
         } else {
             Ok(vm.ctx.not_implemented())
@@ -377,7 +422,7 @@ impl PyInt {
     #[pymethod(name = "__mod__")]
     fn mod_(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
         if objtype::isinstance(&other, &vm.ctx.int_type()) {
-            let other = other.payload::<PyInt>().unwrap();
+            let other = get_py_int(&other);
             inner_mod(self, &other, vm)
         } else {
             Ok(vm.ctx.not_implemented())
@@ -387,7 +432,7 @@ impl PyInt {
     #[pymethod(name = "__rmod__")]
     fn rmod(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
         if objtype::isinstance(&other, &vm.ctx.int_type()) {
-            let other = other.payload::<PyInt>().unwrap();
+            let other = get_py_int(&other);
             inner_mod(&other, self, vm)
         } else {
             Ok(vm.ctx.not_implemented())
@@ -397,15 +442,18 @@ impl PyInt {
     #[pymethod(name = "__divmod__")]
     fn divmod(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
         if objtype::isinstance(&other, &vm.ctx.int_type()) {
-            let v2 = get_value(&other);
-            if *v2 != BigInt::zero() {
-                let (r1, r2) = self.value.div_rem(v2);
-                Ok(vm
-                    .ctx
-                    .new_tuple(vec![vm.ctx.new_int(r1), vm.ctx.new_int(r2)]))
-            } else {
-                Err(vm.new_zero_division_error("integer divmod by zero".to_string()))
-            }
+            let other = get_py_int(&other);
+            inner_divmod(self, &other, vm)
+        } else {
+            Ok(vm.ctx.not_implemented())
+        }
+    }
+
+    #[pymethod(name = "__rdivmod__")]
+    fn rdivmod(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+        if objtype::isinstance(&other, &vm.ctx.int_type()) {
+            let other = get_py_int(&other);
+            inner_divmod(&other, self, vm)
         } else {
             Ok(vm.ctx.not_implemented())
         }
@@ -431,8 +479,29 @@ impl PyInt {
         zelf: PyRef<Self>,
         _precision: OptionalArg<PyObjectRef>,
         _vm: &VirtualMachine,
-    ) -> PyIntRef {
-        zelf
+    ) -> PyResult<PyIntRef> {
+        let _ndigits = match _precision {
+            OptionalArg::Missing => None,
+            OptionalArg::Present(ref value) => {
+                if !_vm.get_none().is(value) {
+                    if !objtype::isinstance(value, &_vm.ctx.int_type()) {
+                        return Err(_vm.new_type_error(format!(
+                            "'{}' object cannot be interpreted as an integer",
+                            value.class().name
+                        )));
+                    };
+                    // Only accept int type _ndigits
+                    let _ndigits = objint::get_value(value);
+                    Some(_ndigits)
+                } else {
+                    return Err(_vm.new_type_error(format!(
+                        "'{}' object cannot be interpreted as an integer",
+                        value.class().name
+                    )));
+                }
+            }
+        };
+        Ok(zelf)
     }
 
     #[pymethod(name = "__int__")]
@@ -644,7 +713,7 @@ impl IntOptions {
     fn get_int_value(self, vm: &VirtualMachine) -> PyResult<BigInt> {
         if let OptionalArg::Present(val) = self.val_options {
             let base = if let OptionalArg::Present(base) = self.base {
-                if !objtype::isinstance(&val, &vm.ctx.str_type) {
+                if !objtype::isinstance(&val, &vm.ctx.str_type()) {
                     return Err(vm.new_type_error(
                         "int() can't convert non-string with explicit base".to_string(),
                     ));
@@ -667,10 +736,16 @@ fn int_new(cls: PyClassRef, options: IntOptions, vm: &VirtualMachine) -> PyResul
 }
 
 // Casting function:
-pub fn to_int(vm: &VirtualMachine, obj: &PyObjectRef, base: u32) -> PyResult<BigInt> {
+pub fn to_int(vm: &VirtualMachine, obj: &PyObjectRef, mut base: u32) -> PyResult<BigInt> {
+    if base == 0 {
+        base = 10
+    } else if base < 2 || base > 36 {
+        return Err(vm.new_value_error("int() base must be >= 2 and <= 36, or 0".to_string()));
+    }
+
     match_class!(obj.clone(),
         s @ PyString => {
-            i32::from_str_radix(s.as_str(), base)
+            i32::from_str_radix(s.as_str().trim(), base)
                 .map(BigInt::from)
                 .map_err(|_|vm.new_value_error(format!(
                     "invalid literal for int() with base {}: '{}'",
@@ -681,7 +756,7 @@ pub fn to_int(vm: &VirtualMachine, obj: &PyObjectRef, base: u32) -> PyResult<Big
             let method = vm.get_method_or_type_error(obj.clone(), "__int__", || {
                 format!("int() argument must be a string or a number, not '{}'", obj.class().name)
             })?;
-            let result = vm.invoke(method, PyFuncArgs::default())?;
+            let result = vm.invoke(&method, PyFuncArgs::default())?;
             match result.payload::<PyInt>() {
                 Some(int_obj) => Ok(int_obj.as_bigint().clone()),
                 None => Err(vm.new_type_error(format!(
@@ -693,11 +768,11 @@ pub fn to_int(vm: &VirtualMachine, obj: &PyObjectRef, base: u32) -> PyResult<Big
 
 // Retrieve inner int value:
 pub fn get_value(obj: &PyObjectRef) -> &BigInt {
-    &obj.payload::<PyInt>().unwrap().value
+    &get_py_int(obj).value
 }
 
 pub fn get_float_value(obj: &PyObjectRef, vm: &VirtualMachine) -> PyResult<f64> {
-    obj.payload::<PyInt>().unwrap().float(vm)
+    get_py_int(obj).float(vm)
 }
 
 #[inline]
@@ -732,9 +807,27 @@ fn div_ints(vm: &VirtualMachine, i1: &BigInt, i2: &BigInt) -> PyResult {
     }
 }
 
+fn get_shift_amount(amount: &PyInt, vm: &VirtualMachine) -> PyResult<usize> {
+    if let Some(n_bits) = amount.value.to_usize() {
+        Ok(n_bits)
+    } else {
+        match &amount.value {
+            v if *v < BigInt::zero() => Err(vm.new_value_error("negative shift count".to_string())),
+            v if *v > BigInt::from(usize::max_value()) => {
+                Err(vm.new_overflow_error("the number is too large to convert to int".to_string()))
+            }
+            _ => panic!("Failed converting {} to rust usize", amount.value),
+        }
+    }
+}
+
+fn get_py_int(obj: &PyObjectRef) -> &PyInt {
+    &obj.payload::<PyInt>().unwrap()
+}
+
 pub fn init(context: &PyContext) {
-    PyInt::extend_class(context, &context.int_type);
-    extend_class!(context, &context.int_type, {
+    PyInt::extend_class(context, &context.types.int_type);
+    extend_class!(context, &context.types.int_type, {
         "__new__" => context.new_rustfunc(int_new),
     });
 }
diff --git a/vm/src/obj/objiter.rs b/vm/src/obj/objiter.rs
index 0fcd078c7..53460acfa 100644
--- a/vm/src/obj/objiter.rs
+++ b/vm/src/obj/objiter.rs
@@ -20,7 +20,7 @@ use super::objtype::PyClassRef;
 pub fn get_iter(vm: &VirtualMachine, iter_target: &PyObjectRef) -> PyResult {
     if let Some(method_or_err) = vm.get_method(iter_target.clone(), "__iter__") {
         let method = method_or_err?;
-        vm.invoke(method, vec![])
+        vm.invoke(&method, vec![])
     } else {
         vm.get_method_or_type_error(iter_target.clone(), "__getitem__", || {
             format!("Cannot iterate over {}", iter_target.class().name)
@@ -122,5 +122,5 @@ impl PySequenceIterator {
 }
 
 pub fn init(context: &PyContext) {
-    PySequenceIterator::extend_class(context, &context.iter_type);
+    PySequenceIterator::extend_class(context, &context.types.iter_type);
 }
diff --git a/vm/src/obj/objlist.rs b/vm/src/obj/objlist.rs
index e9b4b40d5..419cdb45d 100644
--- a/vm/src/obj/objlist.rs
+++ b/vm/src/obj/objlist.rs
@@ -755,7 +755,7 @@ fn do_sort(
     for x in values.iter() {
         keys.push(match &key_func {
             None => x.clone(),
-            Some(ref func) => vm.invoke((*func).clone(), vec![x.clone()])?,
+            Some(ref func) => vm.invoke(func, vec![x.clone()])?,
         });
     }
 
@@ -859,7 +859,7 @@ impl PyListReverseIterator {
 
 #[rustfmt::skip] // to avoid line splitting
 pub fn init(context: &PyContext) {
-    let list_type = &context.list_type;
+    let list_type = &context.types.list_type;
 
     let list_doc = "Built-in mutable sequence.\n\n\
                     If no argument is given, the constructor creates a new empty list.\n\
@@ -901,6 +901,6 @@ pub fn init(context: &PyContext) {
         "remove" => context.new_rustfunc(PyListRef::remove)
     });
 
-    PyListIterator::extend_class(context, &context.listiterator_type);
-    PyListReverseIterator::extend_class(context, &context.listreverseiterator_type);
+    PyListIterator::extend_class(context, &context.types.listiterator_type);
+    PyListReverseIterator::extend_class(context, &context.types.listreverseiterator_type);
 }
diff --git a/vm/src/obj/objmap.rs b/vm/src/obj/objmap.rs
index 61fe67c0d..a27b56e8b 100644
--- a/vm/src/obj/objmap.rs
+++ b/vm/src/obj/objmap.rs
@@ -51,7 +51,7 @@ impl PyMap {
             .collect::<Result<Vec<_>, _>>()?;
 
         // the mapper itself can raise StopIteration which does stop the map iteration
-        vm.invoke(self.mapper.clone(), next_objs)
+        vm.invoke(&self.mapper, next_objs)
     }
 
     #[pymethod(name = "__iter__")]
@@ -61,8 +61,8 @@ impl PyMap {
 }
 
 pub fn init(context: &PyContext) {
-    PyMap::extend_class(context, &context.map_type);
-    extend_class!(context, &context.map_type, {
+    PyMap::extend_class(context, &context.types.map_type);
+    extend_class!(context, &context.types.map_type, {
         "__new__" => context.new_rustfunc(map_new),
     });
 }
diff --git a/vm/src/obj/objmappingproxy.rs b/vm/src/obj/objmappingproxy.rs
index 243a8c89c..b38e9d1ef 100644
--- a/vm/src/obj/objmappingproxy.rs
+++ b/vm/src/obj/objmappingproxy.rs
@@ -13,7 +13,7 @@ pub type PyMappingProxyRef = PyRef<PyMappingProxy>;
 
 impl PyValue for PyMappingProxy {
     fn class(vm: &VirtualMachine) -> PyClassRef {
-        vm.ctx.mappingproxy_type.clone()
+        vm.ctx.types.mappingproxy_type.clone()
     }
 }
 
@@ -38,5 +38,5 @@ impl PyMappingProxy {
 }
 
 pub fn init(context: &PyContext) {
-    PyMappingProxy::extend_class(context, &context.mappingproxy_type)
+    PyMappingProxy::extend_class(context, &context.types.mappingproxy_type)
 }
diff --git a/vm/src/obj/objmemory.rs b/vm/src/obj/objmemory.rs
index 7e1628d13..ed4687032 100644
--- a/vm/src/obj/objmemory.rs
+++ b/vm/src/obj/objmemory.rs
@@ -47,5 +47,5 @@ impl PyValue for PyMemoryView {
 }
 
 pub fn init(ctx: &PyContext) {
-    PyMemoryView::extend_class(ctx, &ctx.memoryview_type)
+    PyMemoryView::extend_class(ctx, &ctx.types.memoryview_type)
 }
diff --git a/vm/src/obj/objmodule.rs b/vm/src/obj/objmodule.rs
index 99dff3b26..902418498 100644
--- a/vm/src/obj/objmodule.rs
+++ b/vm/src/obj/objmodule.rs
@@ -1,6 +1,8 @@
+use crate::function::OptionalOption;
+use crate::obj::objdict::PyDictRef;
 use crate::obj::objstr::PyStringRef;
 use crate::obj::objtype::PyClassRef;
-use crate::pyobject::{PyContext, PyRef, PyResult, PyValue};
+use crate::pyobject::{ItemProtocol, PyContext, PyObjectRef, PyRef, PyResult, PyValue};
 use crate::vm::VirtualMachine;
 
 #[derive(Debug)]
@@ -17,15 +19,71 @@ impl PyValue for PyModule {
     }
 }
 
+pub fn init_module_dict(
+    vm: &VirtualMachine,
+    module_dict: &PyDictRef,
+    name: PyObjectRef,
+    doc: PyObjectRef,
+) {
+    module_dict
+        .set_item("__name__", name, vm)
+        .expect("Failed to set __name__ on module");
+    module_dict
+        .set_item("__doc__", doc, vm)
+        .expect("Failed to set __doc__ on module");
+    module_dict
+        .set_item("__package__", vm.get_none(), vm)
+        .expect("Failed to set __package__ on module");
+    module_dict
+        .set_item("__loader__", vm.get_none(), vm)
+        .expect("Failed to set __loader__ on module");
+    module_dict
+        .set_item("__spec__", vm.get_none(), vm)
+        .expect("Failed to set __spec__ on module");
+}
+
 impl PyModuleRef {
-    fn init(self, name: PyStringRef, vm: &VirtualMachine) -> PyResult {
-        vm.set_attr(&self.into_object(), "__name__", name)?;
-        Ok(vm.get_none())
+    fn new(
+        cls: PyClassRef,
+        name: PyStringRef,
+        doc: OptionalOption<PyStringRef>,
+        vm: &VirtualMachine,
+    ) -> PyResult<PyModuleRef> {
+        let zelf = PyModule {
+            name: name.as_str().to_owned(),
+        }
+        .into_ref_with_type(vm, cls)?;
+        init_module_dict(
+            vm,
+            zelf.as_object().dict.as_ref().unwrap(),
+            name.into_object(),
+            doc.flat_option()
+                .map_or_else(|| vm.get_none(), PyRef::into_object),
+        );
+        Ok(zelf)
+    }
+
+    fn getattribute(self, name: PyStringRef, vm: &VirtualMachine) -> PyResult {
+        vm.generic_getattribute(self.as_object().clone(), name.clone())?
+            .ok_or_else(|| {
+                vm.new_attribute_error(format!(
+                    "module '{}' has no attribute '{}'",
+                    self.name, name,
+                ))
+            })
+    }
+
+    fn repr(self, vm: &VirtualMachine) -> PyResult {
+        let importlib = vm.import("_frozen_importlib", &vm.ctx.new_tuple(vec![]), 0)?;
+        let module_repr = vm.get_attribute(importlib, "_module_repr")?;
+        vm.invoke(&module_repr, vec![self.into_object()])
     }
 }
 
 pub fn init(context: &PyContext) {
-    extend_class!(&context, &context.module_type, {
-        "__init__" => context.new_rustfunc(PyModuleRef::init),
+    extend_class!(&context, &context.types.module_type, {
+        "__new__" => context.new_rustfunc(PyModuleRef::new),
+        "__getattribute__" => context.new_rustfunc(PyModuleRef::getattribute),
+        "__repr__" => context.new_rustfunc(PyModuleRef::repr),
     });
 }
diff --git a/vm/src/obj/objnamespace.rs b/vm/src/obj/objnamespace.rs
index f8bfc9369..7ef304c1e 100644
--- a/vm/src/obj/objnamespace.rs
+++ b/vm/src/obj/objnamespace.rs
@@ -28,5 +28,5 @@ impl PyNamespace {
 }
 
 pub fn init(context: &PyContext) {
-    PyNamespace::extend_class(context, &context.namespace_type);
+    PyNamespace::extend_class(context, &context.types.namespace_type);
 }
diff --git a/vm/src/obj/objnone.rs b/vm/src/obj/objnone.rs
index fa23ca1b0..cf1b4d3a5 100644
--- a/vm/src/obj/objnone.rs
+++ b/vm/src/obj/objnone.rs
@@ -64,7 +64,7 @@ impl PyNoneRef {
             if let Ok(property) = PyPropertyRef::try_from_object(vm, descriptor.clone()) {
                 property.instance_binding_get(obj, vm)
             } else {
-                vm.invoke(get_func, vec![descriptor, obj, cls])
+                vm.invoke(&get_func, vec![descriptor, obj, cls])
             }
         }
 
@@ -95,7 +95,7 @@ impl PyNoneRef {
                 Ok(attr)
             }
         } else if let Some(getter) = class_get_attr(&cls, "__getattr__") {
-            vm.invoke(getter, vec![self.into_object(), name.into_object()])
+            vm.invoke(&getter, vec![self.into_object(), name.into_object()])
         } else {
             Err(vm.new_attribute_error(format!("{} has no attribute '{}'", self.as_object(), name)))
         }
diff --git a/vm/src/obj/objobject.rs b/vm/src/obj/objobject.rs
index 8f2408dba..87b1da34a 100644
--- a/vm/src/obj/objobject.rs
+++ b/vm/src/obj/objobject.rs
@@ -24,7 +24,7 @@ impl PyValue for PyInstance {
 pub fn new_instance(vm: &VirtualMachine, mut args: PyFuncArgs) -> PyResult {
     // more or less __new__ operator
     let cls = PyClassRef::try_from_object(vm, args.shift())?;
-    let dict = if cls.is(&vm.ctx.object) {
+    let dict = if cls.is(&vm.ctx.object()) {
         None
     } else {
         Some(vm.ctx.new_dict())
@@ -72,7 +72,7 @@ fn object_setattr(
     if let Some(attr) = objtype::class_get_attr(&cls, &attr_name.value) {
         if let Some(descriptor) = objtype::class_get_attr(&attr.class(), "__set__") {
             return vm
-                .invoke(descriptor, vec![attr, obj.clone(), value])
+                .invoke(&descriptor, vec![attr, obj.clone(), value])
                 .map(|_| ());
         }
     }
@@ -94,7 +94,7 @@ fn object_delattr(obj: PyObjectRef, attr_name: PyStringRef, vm: &VirtualMachine)
 
     if let Some(attr) = objtype::class_get_attr(&cls, &attr_name.value) {
         if let Some(descriptor) = objtype::class_get_attr(&attr.class(), "__delete__") {
-            return vm.invoke(descriptor, vec![attr, obj.clone()]).map(|_| ());
+            return vm.invoke(&descriptor, vec![attr, obj.clone()]).map(|_| ());
         }
     }
 
@@ -118,6 +118,10 @@ fn object_repr(zelf: PyObjectRef, _vm: &VirtualMachine) -> String {
     format!("<{} object at 0x{:x}>", zelf.class().name, zelf.get_id())
 }
 
+fn object_subclasshook(vm: &VirtualMachine, _args: PyFuncArgs) -> PyResult {
+    Ok(vm.ctx.not_implemented())
+}
+
 pub fn object_dir(obj: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyList> {
     let attributes: PyAttributes = objtype::get_attributes(obj.class());
 
@@ -126,7 +130,7 @@ pub fn object_dir(obj: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyList> {
     // Get instance attributes:
     if let Some(object_dict) = &obj.dict {
         vm.invoke(
-            vm.get_attribute(dict.clone().into_object(), "update")?,
+            &vm.get_attribute(dict.clone().into_object(), "update")?,
             object_dict.clone().into_object(),
         )?;
     }
@@ -149,7 +153,7 @@ fn object_format(
 }
 
 pub fn init(context: &PyContext) {
-    let object = &context.object;
+    let object = &context.types.object_type;
     let object_doc = "The most base type";
 
     extend_class!(context, object, {
@@ -179,7 +183,8 @@ pub fn init(context: &PyContext) {
         "__repr__" => context.new_rustfunc(object_repr),
         "__format__" => context.new_rustfunc(object_format),
         "__getattribute__" => context.new_rustfunc(object_getattribute),
-        "__doc__" => context.new_str(object_doc.to_string())
+        "__subclasshook__" => context.new_classmethod(object_subclasshook),
+        "__doc__" => context.new_str(object_doc.to_string()),
     });
 }
 
@@ -218,39 +223,8 @@ fn object_dict_setter(
     ))
 }
 
-fn object_getattribute(obj: PyObjectRef, name_str: PyStringRef, vm: &VirtualMachine) -> PyResult {
-    let name = &name_str.value;
+fn object_getattribute(obj: PyObjectRef, name: PyStringRef, vm: &VirtualMachine) -> PyResult {
     vm_trace!("object.__getattribute__({:?}, {:?})", obj, name);
-    let cls = obj.class();
-
-    if let Some(attr) = objtype::class_get_attr(&cls, &name) {
-        let attr_class = attr.class();
-        if objtype::class_has_attr(&attr_class, "__set__") {
-            if let Some(descriptor) = objtype::class_get_attr(&attr_class, "__get__") {
-                return vm.invoke(descriptor, vec![attr, obj, cls.into_object()]);
-            }
-        }
-    }
-
-    if let Some(obj_attr) = object_getattr(&obj, &name, &vm)? {
-        Ok(obj_attr)
-    } else if let Some(attr) = objtype::class_get_attr(&cls, &name) {
-        vm.call_get_descriptor(attr, obj)
-    } else if let Some(getter) = objtype::class_get_attr(&cls, "__getattr__") {
-        vm.invoke(getter, vec![obj, name_str.into_object()])
-    } else {
-        Err(vm.new_attribute_error(format!("{} has no attribute '{}'", obj, name)))
-    }
-}
-
-fn object_getattr(
-    obj: &PyObjectRef,
-    attr_name: &str,
-    vm: &VirtualMachine,
-) -> PyResult<Option<PyObjectRef>> {
-    if let Some(ref dict) = obj.dict {
-        dict.get_item_option(attr_name, vm)
-    } else {
-        Ok(None)
-    }
+    vm.generic_getattribute(obj.clone(), name.clone())?
+        .ok_or_else(|| vm.new_attribute_error(format!("{} has no attribute '{}'", obj, name)))
 }
diff --git a/vm/src/obj/objproperty.rs b/vm/src/obj/objproperty.rs
index 9c8394a4c..a6d5bcfa1 100644
--- a/vm/src/obj/objproperty.rs
+++ b/vm/src/obj/objproperty.rs
@@ -1,7 +1,6 @@
 /*! Python `property` descriptor class.
 
 */
-
 use crate::function::{IntoPyNativeFunc, OptionalArg, PyFuncArgs};
 use crate::obj::objtype::PyClassRef;
 use crate::pyobject::{
@@ -9,6 +8,7 @@ use crate::pyobject::{
     TypeProtocol,
 };
 use crate::vm::VirtualMachine;
+use std::cell::RefCell;
 
 // Read-only property, doesn't have __set__ or __delete__
 #[pyclass]
@@ -37,7 +37,7 @@ impl PyReadOnlyProperty {
         if obj.is(vm.ctx.none.as_object()) {
             Ok(zelf.into_object())
         } else {
-            vm.invoke(zelf.getter.clone(), obj)
+            vm.invoke(&zelf.getter, obj)
         }
     }
 }
@@ -80,7 +80,7 @@ pub struct PyProperty {
     getter: Option<PyObjectRef>,
     setter: Option<PyObjectRef>,
     deleter: Option<PyObjectRef>,
-    doc: Option<PyObjectRef>,
+    doc: RefCell<Option<PyObjectRef>>,
 }
 
 impl PyValue for PyProperty {
@@ -107,20 +107,14 @@ impl PyProperty {
         );
 
         fn into_option(vm: &VirtualMachine, arg: Option<&PyObjectRef>) -> Option<PyObjectRef> {
-            arg.and_then(|arg| {
-                if vm.ctx.none().is(arg) {
-                    None
-                } else {
-                    Some(arg.clone())
-                }
-            })
+            arg.and_then(|arg| py_none_to_option(vm, arg))
         }
 
         PyProperty {
             getter: into_option(vm, fget),
             setter: into_option(vm, fset),
             deleter: into_option(vm, fdel),
-            doc: into_option(vm, doc),
+            doc: RefCell::new(into_option(vm, doc)),
         }
         .into_ref_with_type(vm, cls)
     }
@@ -129,8 +123,8 @@ impl PyProperty {
 
     // specialised version that doesn't check for None
     pub(crate) fn instance_binding_get(&self, obj: PyObjectRef, vm: &VirtualMachine) -> PyResult {
-        if let Some(getter) = self.getter.as_ref() {
-            vm.invoke(getter.clone(), obj)
+        if let Some(ref getter) = self.getter.as_ref() {
+            vm.invoke(getter, obj)
         } else {
             Err(vm.new_attribute_error("unreadable attribute".to_string()))
         }
@@ -147,7 +141,7 @@ impl PyProperty {
             if obj.is(vm.ctx.none.as_object()) {
                 Ok(zelf.into_object())
             } else {
-                vm.invoke(getter.clone(), obj)
+                vm.invoke(&getter, obj)
             }
         } else {
             Err(vm.new_attribute_error("unreadable attribute".to_string()))
@@ -156,8 +150,8 @@ impl PyProperty {
 
     #[pymethod(name = "__set__")]
     fn set(&self, obj: PyObjectRef, value: PyObjectRef, vm: &VirtualMachine) -> PyResult {
-        if let Some(setter) = self.setter.as_ref() {
-            vm.invoke(setter.clone(), vec![obj, value])
+        if let Some(ref setter) = self.setter.as_ref() {
+            vm.invoke(setter, vec![obj, value])
         } else {
             Err(vm.new_attribute_error("can't set attribute".to_string()))
         }
@@ -165,8 +159,8 @@ impl PyProperty {
 
     #[pymethod(name = "__delete__")]
     fn delete(&self, obj: PyObjectRef, vm: &VirtualMachine) -> PyResult {
-        if let Some(deleter) = self.deleter.as_ref() {
-            vm.invoke(deleter.clone(), obj)
+        if let Some(ref deleter) = self.deleter.as_ref() {
+            vm.invoke(deleter, obj)
         } else {
             Err(vm.new_attribute_error("can't delete attribute".to_string()))
         }
@@ -189,6 +183,15 @@ impl PyProperty {
         self.deleter.clone()
     }
 
+    fn doc_getter(&self, _vm: &VirtualMachine) -> Option<PyObjectRef> {
+        self.doc.borrow().clone()
+    }
+
+    fn doc_setter(&self, value: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+        self.doc.replace(py_none_to_option(vm, &value));
+        Ok(vm.get_none())
+    }
+
     // Python builder functions
 
     #[pymethod]
@@ -201,7 +204,7 @@ impl PyProperty {
             getter: getter.or_else(|| zelf.getter.clone()),
             setter: zelf.setter.clone(),
             deleter: zelf.deleter.clone(),
-            doc: None,
+            doc: RefCell::new(None),
         }
         .into_ref_with_type(vm, TypeProtocol::class(&zelf))
     }
@@ -216,7 +219,7 @@ impl PyProperty {
             getter: zelf.getter.clone(),
             setter: setter.or_else(|| zelf.setter.clone()),
             deleter: zelf.deleter.clone(),
-            doc: None,
+            doc: RefCell::new(None),
         }
         .into_ref_with_type(vm, TypeProtocol::class(&zelf))
     }
@@ -231,12 +234,21 @@ impl PyProperty {
             getter: zelf.getter.clone(),
             setter: zelf.setter.clone(),
             deleter: deleter.or_else(|| zelf.deleter.clone()),
-            doc: None,
+            doc: RefCell::new(None),
         }
         .into_ref_with_type(vm, TypeProtocol::class(&zelf))
     }
 }
 
+/// Take a python object and turn it into an option object, where python None maps to rust None.
+fn py_none_to_option(vm: &VirtualMachine, value: &PyObjectRef) -> Option<PyObjectRef> {
+    if vm.ctx.none().is(value) {
+        None
+    } else {
+        Some(value.clone())
+    }
+}
+
 pub struct PropertyBuilder<'a> {
     ctx: &'a PyContext,
     getter: Option<PyObjectRef>,
@@ -276,7 +288,7 @@ impl<'a> PropertyBuilder<'a> {
                 getter: self.getter.clone(),
                 setter: self.setter.clone(),
                 deleter: None,
-                doc: None,
+                doc: RefCell::new(None),
             };
 
             PyObject::new(payload, self.ctx.property_type(), None)
@@ -293,6 +305,16 @@ impl<'a> PropertyBuilder<'a> {
 }
 
 pub fn init(context: &PyContext) {
-    PyReadOnlyProperty::extend_class(context, &context.readonly_property_type);
-    PyProperty::extend_class(context, &context.property_type);
+    PyReadOnlyProperty::extend_class(context, &context.types.readonly_property_type);
+    PyProperty::extend_class(context, &context.types.property_type);
+
+    // This is a bit unfortunate, but this instance attribute overlaps with the
+    // class __doc__ string..
+    extend_class!(context, &context.types.property_type, {
+        "__doc__" =>
+        PropertyBuilder::new(context)
+            .add_getter(PyProperty::doc_getter)
+            .add_setter(PyProperty::doc_setter)
+            .create(),
+    });
 }
diff --git a/vm/src/obj/objrange.rs b/vm/src/obj/objrange.rs
index 905550f50..99584a292 100644
--- a/vm/src/obj/objrange.rs
+++ b/vm/src/obj/objrange.rs
@@ -105,8 +105,8 @@ pub fn get_value(obj: &PyObjectRef) -> PyRange {
 }
 
 pub fn init(context: &PyContext) {
-    PyRange::extend_class(context, &context.range_type);
-    PyRangeIterator::extend_class(context, &context.rangeiterator_type);
+    PyRange::extend_class(context, &context.types.range_type);
+    PyRangeIterator::extend_class(context, &context.types.rangeiterator_type);
 }
 
 type PyRangeRef = PyRef<PyRange>;
diff --git a/vm/src/obj/objset.rs b/vm/src/obj/objset.rs
index cfa8e1701..dc4a3ca95 100644
--- a/vm/src/obj/objset.rs
+++ b/vm/src/obj/objset.rs
@@ -748,6 +748,6 @@ impl TryFromObject for SetIterable {
 }
 
 pub fn init(context: &PyContext) {
-    PySet::extend_class(context, &context.set_type);
-    PyFrozenSet::extend_class(context, &context.frozenset_type);
+    PySet::extend_class(context, &context.types.set_type);
+    PyFrozenSet::extend_class(context, &context.types.frozenset_type);
 }
diff --git a/vm/src/obj/objslice.rs b/vm/src/obj/objslice.rs
index 82e4cef8c..0de224d36 100644
--- a/vm/src/obj/objslice.rs
+++ b/vm/src/obj/objslice.rs
@@ -114,7 +114,7 @@ fn to_index_value(vm: &VirtualMachine, obj: &PyObjectRef) -> PyResult<Option<Big
 }
 
 pub fn init(context: &PyContext) {
-    let slice_type = &context.slice_type;
+    let slice_type = &context.types.slice_type;
 
     extend_class!(context, slice_type, {
         "__new__" => context.new_rustfunc(slice_new),
diff --git a/vm/src/obj/objstaticmethod.rs b/vm/src/obj/objstaticmethod.rs
index a33acf176..e330652a5 100644
--- a/vm/src/obj/objstaticmethod.rs
+++ b/vm/src/obj/objstaticmethod.rs
@@ -32,7 +32,7 @@ impl PyStaticMethodRef {
 }
 
 pub fn init(context: &PyContext) {
-    let staticmethod_type = &context.staticmethod_type;
+    let staticmethod_type = &context.types.staticmethod_type;
     extend_class!(context, staticmethod_type, {
         "__get__" => context.new_rustfunc(PyStaticMethodRef::get),
         "__new__" => context.new_rustfunc(PyStaticMethodRef::new),
diff --git a/vm/src/obj/objstr.rs b/vm/src/obj/objstr.rs
index ff609eaad..96949553c 100644
--- a/vm/src/obj/objstr.rs
+++ b/vm/src/obj/objstr.rs
@@ -28,6 +28,7 @@ use crate::vm::VirtualMachine;
 
 use super::objbytes::PyBytes;
 use super::objdict::PyDict;
+use super::objfloat;
 use super::objint::{self, PyInt};
 use super::objiter;
 use super::objnone::PyNone;
@@ -514,10 +515,15 @@ impl PyString {
     fn modulo(&self, values: PyObjectRef, vm: &VirtualMachine) -> PyResult {
         let format_string_text = &self.value;
         let format_string = CFormatString::from_str(format_string_text)
-            .map_err(|err| vm.new_value_error(format!("{}", err)))?;
+            .map_err(|err| vm.new_value_error(err.to_string()))?;
         do_cformat(vm, format_string, values.clone())
     }
 
+    #[pymethod(name = "__rmod__")]
+    fn rmod(&self, _values: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+        Ok(vm.ctx.not_implemented())
+    }
+
     #[pymethod]
     fn format(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
         if args.args.is_empty() {
@@ -1145,10 +1151,10 @@ impl IntoPyObject for &String {
 }
 
 pub fn init(ctx: &PyContext) {
-    PyString::extend_class(ctx, &ctx.str_type);
+    PyString::extend_class(ctx, &ctx.types.str_type);
 
-    PyStringIterator::extend_class(ctx, &ctx.striterator_type);
-    PyStringReverseIterator::extend_class(ctx, &ctx.strreverseiterator_type);
+    PyStringIterator::extend_class(ctx, &ctx.types.striterator_type);
+    PyStringReverseIterator::extend_class(ctx, &ctx.types.strreverseiterator_type);
 }
 
 pub fn get_value(obj: &PyObjectRef) -> String {
@@ -1220,6 +1226,21 @@ fn do_cformat_specifier(
             }
             Ok(format_spec.format_number(objint::get_value(&obj)))
         }
+        CFormatType::Float(_) => {
+            if objtype::isinstance(&obj, &vm.ctx.float_type()) {
+                Ok(format_spec.format_float(objfloat::get_value(&obj)))
+            } else if objtype::isinstance(&obj, &vm.ctx.int_type()) {
+                Ok(format_spec.format_float(objint::get_value(&obj).to_f64().unwrap()))
+            } else {
+                let required_type_string = "an floating point or integer";
+                Err(vm.new_type_error(format!(
+                    "%{} format: {} is required, not {}",
+                    format_spec.format_char,
+                    required_type_string,
+                    obj.class()
+                )))
+            }
+        }
         CFormatType::Character => {
             let char_string = {
                 if objtype::isinstance(&obj, &vm.ctx.int_type()) {
@@ -1246,10 +1267,6 @@ fn do_cformat_specifier(
             format_spec.precision = Some(CFormatQuantity::Amount(1));
             Ok(format_spec.format_string(char_string))
         }
-        _ => Err(vm.new_not_implemented_error(format!(
-            "Not yet implemented for %{}",
-            format_spec.format_char
-        ))),
     }
 }
 
@@ -1312,9 +1329,9 @@ fn do_cformat(
     } else {
         // check for only literal parts, in which case only dict or empty tuple is allowed
         if num_specifiers == 0
-            && !(objtype::isinstance(&values_obj, &vm.ctx.tuple_type)
+            && !(objtype::isinstance(&values_obj, &vm.ctx.types.tuple_type)
                 && objtuple::get_value(&values_obj).is_empty())
-            && !objtype::isinstance(&values_obj, &vm.ctx.dict_type)
+            && !objtype::isinstance(&values_obj, &vm.ctx.types.dict_type)
         {
             return Err(vm.new_type_error(
                 "not all arguments converted during string formatting".to_string(),
@@ -1380,7 +1397,7 @@ fn do_cformat(
             .into_iter()
             .nth(tuple_index)
             .is_some())
-        && !objtype::isinstance(&values_obj, &vm.ctx.dict_type)
+        && !objtype::isinstance(&values_obj, &vm.ctx.types.dict_type)
     {
         return Err(
             vm.new_type_error("not all arguments converted during string formatting".to_string())
diff --git a/vm/src/obj/objsuper.rs b/vm/src/obj/objsuper.rs
index a9fb668cb..eedd3a71c 100644
--- a/vm/src/obj/objsuper.rs
+++ b/vm/src/obj/objsuper.rs
@@ -24,6 +24,7 @@ pub type PySuperRef = PyRef<PySuper>;
 pub struct PySuper {
     obj: PyObjectRef,
     typ: PyObjectRef,
+    obj_type: PyObjectRef,
 }
 
 impl PyValue for PySuper {
@@ -33,7 +34,7 @@ impl PyValue for PySuper {
 }
 
 pub fn init(context: &PyContext) {
-    let super_type = &context.super_type;
+    let super_type = &context.types.super_type;
 
     let super_doc = "super() -> same as super(__class__, <first argument>)\n\
                      super(type) -> unbound super object\n\
@@ -53,9 +54,31 @@ pub fn init(context: &PyContext) {
         "__new__" => context.new_rustfunc(super_new),
         "__getattribute__" => context.new_rustfunc(super_getattribute),
         "__doc__" => context.new_str(super_doc.to_string()),
+        "__str__" => context.new_rustfunc(super_str),
+        "__repr__" => context.new_rustfunc(super_repr),
     });
 }
 
+fn super_str(zelf: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+    vm.call_method(&zelf, "__repr__", vec![])
+}
+
+fn super_repr(zelf: PyObjectRef, _vm: &VirtualMachine) -> String {
+    let super_obj = zelf.downcast::<PySuper>().unwrap();
+    let class_type_str = if let Ok(type_class) = super_obj.typ.clone().downcast::<PyClass>() {
+        type_class.name.clone()
+    } else {
+        "NONE".to_string()
+    };
+    match super_obj.obj_type.clone().downcast::<PyClass>() {
+        Ok(obj_class_typ) => format!(
+            "<super: <class '{}'>, <{} object>>",
+            class_type_str, obj_class_typ.name
+        ),
+        _ => format!("<super: <class '{}'> NULL>", class_type_str),
+    }
+}
+
 fn super_getattribute(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
     arg_check!(
         vm,
@@ -141,7 +164,7 @@ fn super_new(
     };
 
     // Check obj type:
-    if !objtype::isinstance(&py_obj, &py_type) {
+    let obj_type = if !objtype::isinstance(&py_obj, &py_type) {
         let is_subclass = if let Ok(py_obj) = PyClassRef::try_from_object(vm, py_obj.clone()) {
             objtype::issubclass(&py_obj, &py_type)
         } else {
@@ -152,11 +175,15 @@ fn super_new(
                 "super(type, obj): obj must be an instance or subtype of type".to_string(),
             ));
         }
-    }
+        PyClassRef::try_from_object(vm, py_obj.clone())?
+    } else {
+        py_obj.class()
+    };
 
     PySuper {
         obj: py_obj,
         typ: py_type.into_object(),
+        obj_type: obj_type.into_object(),
     }
     .into_ref_with_type(vm, cls)
 }
diff --git a/vm/src/obj/objtuple.rs b/vm/src/obj/objtuple.rs
index e13d3160f..459f0e9bc 100644
--- a/vm/src/obj/objtuple.rs
+++ b/vm/src/obj/objtuple.rs
@@ -3,7 +3,9 @@ use std::fmt;
 
 use crate::function::OptionalArg;
 use crate::pyhash;
-use crate::pyobject::{IdProtocol, PyClassImpl, PyContext, PyObjectRef, PyRef, PyResult, PyValue};
+use crate::pyobject::{
+    IdProtocol, IntoPyObject, PyClassImpl, PyContext, PyObjectRef, PyRef, PyResult, PyValue,
+};
 use crate::vm::{ReprGuard, VirtualMachine};
 
 use super::objbool;
@@ -37,6 +39,27 @@ impl PyValue for PyTuple {
     }
 }
 
+impl<A> IntoPyObject for (A,)
+where
+    A: IntoPyObject,
+{
+    fn into_pyobject(self, vm: &VirtualMachine) -> PyResult {
+        Ok(vm.ctx.new_tuple(vec![self.0.into_pyobject(vm)?]))
+    }
+}
+
+impl<A, B> IntoPyObject for (A, B)
+where
+    A: IntoPyObject,
+    B: IntoPyObject,
+{
+    fn into_pyobject(self, vm: &VirtualMachine) -> PyResult {
+        Ok(vm
+            .ctx
+            .new_tuple(vec![self.0.into_pyobject(vm)?, self.1.into_pyobject(vm)?]))
+    }
+}
+
 impl PyTuple {
     pub fn fast_getitem(&self, idx: usize) -> PyObjectRef {
         self.elements[idx].clone()
@@ -253,7 +276,7 @@ impl PyTupleIterator {
 
 #[rustfmt::skip] // to avoid line splitting
 pub fn init(context: &PyContext) {
-    let tuple_type = &context.tuple_type;
+    let tuple_type = &context.types.tuple_type;
     let tuple_doc = "tuple() -> empty tuple
 tuple(iterable) -> tuple initialized from iterable's items
 
@@ -280,5 +303,5 @@ If the argument is a tuple, the return value is the same object.";
         "index" => context.new_rustfunc(PyTupleRef::index)
     });
 
-    PyTupleIterator::extend_class(context, &context.tupleiterator_type);
+    PyTupleIterator::extend_class(context, &context.types.tupleiterator_type);
 }
diff --git a/vm/src/obj/objtype.rs b/vm/src/obj/objtype.rs
index 9df1a829f..68b2feba6 100644
--- a/vm/src/obj/objtype.rs
+++ b/vm/src/obj/objtype.rs
@@ -137,7 +137,7 @@ impl PyClassRef {
         if let Some(attr) = class_get_attr(&mcl, &name) {
             let attr_class = attr.class();
             if class_has_attr(&attr_class, "__set__") {
-                if let Some(descriptor) = class_get_attr(&attr_class, "__get__") {
+                if let Some(ref descriptor) = class_get_attr(&attr_class, "__get__") {
                     return vm.invoke(
                         descriptor,
                         vec![attr, self.into_object(), mcl.into_object()],
@@ -148,7 +148,7 @@ impl PyClassRef {
 
         if let Some(attr) = class_get_attr(&self, &name) {
             let attr_class = attr.class();
-            if let Some(descriptor) = class_get_attr(&attr_class, "__get__") {
+            if let Some(ref descriptor) = class_get_attr(&attr_class, "__get__") {
                 let none = vm.get_none();
                 return vm.invoke(descriptor, vec![attr, none, self.into_object()]);
             }
@@ -158,7 +158,7 @@ impl PyClassRef {
             Ok(cls_attr)
         } else if let Some(attr) = class_get_attr(&mcl, &name) {
             vm.call_get_descriptor(attr, self.into_object())
-        } else if let Some(getter) = class_get_attr(&self, "__getattr__") {
+        } else if let Some(ref getter) = class_get_attr(&self, "__getattr__") {
             vm.invoke(getter, vec![mcl.into_object(), name_ref.into_object()])
         } else {
             Err(vm.new_attribute_error(format!("{} has no attribute '{}'", self, name)))
@@ -172,7 +172,7 @@ impl PyClassRef {
         vm: &VirtualMachine,
     ) -> PyResult<()> {
         if let Some(attr) = class_get_attr(&self.class(), &attr_name.value) {
-            if let Some(descriptor) = class_get_attr(&attr.class(), "__set__") {
+            if let Some(ref descriptor) = class_get_attr(&attr.class(), "__set__") {
                 vm.invoke(descriptor, vec![attr, self.into_object(), value])?;
                 return Ok(());
             }
@@ -212,7 +212,7 @@ pub fn init(ctx: &PyContext) {
                     type(object) -> the object's type\n\
                     type(name, bases, dict) -> a new type";
 
-    extend_class!(&ctx, &ctx.type_type, {
+    extend_class!(&ctx, &ctx.types.type_type, {
         "__call__" => ctx.new_rustfunc(type_call),
         "__dict__" =>
         PropertyBuilder::new(ctx)
@@ -288,11 +288,11 @@ pub fn type_call(class: PyClassRef, args: Args, kwargs: KwArgs, vm: &VirtualMach
     vm_trace!("type_call: {:?}", class);
     let new = class_get_attr(&class, "__new__").expect("All types should have a __new__.");
     let new_wrapped = vm.call_get_descriptor(new, class.into_object())?;
-    let obj = vm.invoke(new_wrapped, (&args, &kwargs))?;
+    let obj = vm.invoke(&new_wrapped, (&args, &kwargs))?;
 
     if let Some(init_method_or_err) = vm.get_method(obj.clone(), "__init__") {
         let init_method = init_method_or_err?;
-        let res = vm.invoke(init_method, (&args, &kwargs))?;
+        let res = vm.invoke(&init_method, (&args, &kwargs))?;
         if !res.is(&vm.get_none()) {
             return Err(vm.new_type_error("__init__ must return None".to_string()));
         }
@@ -433,8 +433,8 @@ mod tests {
     #[test]
     fn test_linearise() {
         let context = PyContext::new();
-        let object: PyClassRef = context.object.clone();
-        let type_type = &context.type_type;
+        let object: PyClassRef = context.object();
+        let type_type = &context.types.type_type;
 
         let a = new(type_type.clone(), "A", vec![object.clone()], HashMap::new()).unwrap();
         let b = new(type_type.clone(), "B", vec![object.clone()], HashMap::new()).unwrap();
diff --git a/vm/src/obj/objweakproxy.rs b/vm/src/obj/objweakproxy.rs
index 5d4f68d9d..f510a03ef 100644
--- a/vm/src/obj/objweakproxy.rs
+++ b/vm/src/obj/objweakproxy.rs
@@ -61,5 +61,5 @@ impl PyWeakProxy {
 }
 
 pub fn init(context: &PyContext) {
-    PyWeakProxy::extend_class(&context, &context.weakproxy_type);
+    PyWeakProxy::extend_class(&context, &context.types.weakproxy_type);
 }
diff --git a/vm/src/obj/objweakref.rs b/vm/src/obj/objweakref.rs
index b3b7e03c9..ae4375cd0 100644
--- a/vm/src/obj/objweakref.rs
+++ b/vm/src/obj/objweakref.rs
@@ -48,7 +48,7 @@ impl PyWeakRef {
 }
 
 pub fn init(context: &PyContext) {
-    extend_class!(context, &context.weakref_type, {
+    extend_class!(context, &context.types.weakref_type, {
         "__new__" => context.new_rustfunc(PyWeakRef::create),
         "__call__" => context.new_rustfunc(PyWeakRef::call)
     });
diff --git a/vm/src/obj/objzip.rs b/vm/src/obj/objzip.rs
index d9c577aa0..0223b8bf2 100644
--- a/vm/src/obj/objzip.rs
+++ b/vm/src/obj/objzip.rs
@@ -51,8 +51,8 @@ impl PyZip {
 }
 
 pub fn init(context: &PyContext) {
-    PyZip::extend_class(context, &context.zip_type);
-    extend_class!(context, &context.zip_type, {
+    PyZip::extend_class(context, &context.types.zip_type);
+    extend_class!(context, &context.types.zip_type, {
         "__new__" => context.new_rustfunc(zip_new),
     });
 }
diff --git a/vm/src/pyobject.rs b/vm/src/pyobject.rs
index ba40d5473..05049528c 100644
--- a/vm/src/pyobject.rs
+++ b/vm/src/pyobject.rs
@@ -1,12 +1,9 @@
 use std::any::Any;
 use std::cell::Cell;
-use std::cell::RefCell;
 use std::collections::HashMap;
 use std::fmt;
 use std::marker::PhantomData;
-use std::mem;
 use std::ops::Deref;
-use std::ptr;
 use std::rc::Rc;
 
 use num_bigint::BigInt;
@@ -16,46 +13,30 @@ use num_traits::{One, Zero};
 use crate::bytecode;
 use crate::exceptions;
 use crate::function::{IntoPyNativeFunc, PyFuncArgs};
-use crate::obj::objbool;
 use crate::obj::objbuiltinfunc::PyBuiltinFunction;
 use crate::obj::objbytearray;
 use crate::obj::objbytes;
-use crate::obj::objclassmethod::{self, PyClassMethod};
+use crate::obj::objclassmethod::PyClassMethod;
 use crate::obj::objcode;
 use crate::obj::objcode::PyCodeRef;
-use crate::obj::objcomplex::{self, PyComplex};
-use crate::obj::objdict::{self, PyDict, PyDictRef};
-use crate::obj::objellipsis;
-use crate::obj::objenumerate;
-use crate::obj::objfilter;
-use crate::obj::objfloat::{self, PyFloat};
-use crate::obj::objframe;
-use crate::obj::objfunction::{self, PyFunction, PyMethod};
-use crate::obj::objgenerator;
-use crate::obj::objint::{self, PyInt, PyIntRef};
+use crate::obj::objcomplex::PyComplex;
+use crate::obj::objdict::{PyDict, PyDictRef};
+use crate::obj::objfloat::PyFloat;
+use crate::obj::objfunction::{PyFunction, PyMethod};
+use crate::obj::objint::{PyInt, PyIntRef};
 use crate::obj::objiter;
-use crate::obj::objlist::{self, PyList};
-use crate::obj::objmap;
-use crate::obj::objmappingproxy;
-use crate::obj::objmemory;
-use crate::obj::objmodule::{self, PyModule};
-use crate::obj::objnamespace::{self, PyNamespace};
-use crate::obj::objnone::{self, PyNone, PyNoneRef};
+use crate::obj::objlist::PyList;
+use crate::obj::objmodule::PyModule;
+use crate::obj::objnamespace::PyNamespace;
+use crate::obj::objnone::{PyNone, PyNoneRef};
 use crate::obj::objobject;
-use crate::obj::objproperty;
 use crate::obj::objproperty::PropertyBuilder;
-use crate::obj::objrange;
-use crate::obj::objset::{self, PySet};
-use crate::obj::objslice;
-use crate::obj::objstaticmethod;
+use crate::obj::objset::PySet;
 use crate::obj::objstr;
-use crate::obj::objsuper;
-use crate::obj::objtuple::{self, PyTuple, PyTupleRef};
+use crate::obj::objtuple::{PyTuple, PyTupleRef};
 use crate::obj::objtype::{self, PyClass, PyClassRef};
-use crate::obj::objweakproxy;
-use crate::obj::objweakref;
-use crate::obj::objzip;
 use crate::scope::Scope;
+use crate::types::{create_type, initialize_types, TypeZoo};
 use crate::vm::VirtualMachine;
 use indexmap::IndexMap;
 
@@ -112,71 +93,16 @@ impl fmt::Display for PyObject<dyn PyObjectPayload> {
 
 #[derive(Debug)]
 pub struct PyContext {
-    pub bytes_type: PyClassRef,
-    pub bytesiterator_type: PyClassRef,
-    pub bytearray_type: PyClassRef,
-    pub bytearrayiterator_type: PyClassRef,
-    pub bool_type: PyClassRef,
-    pub classmethod_type: PyClassRef,
-    pub code_type: PyClassRef,
-    pub dict_type: PyClassRef,
-    pub ellipsis_type: PyClassRef,
-    pub enumerate_type: PyClassRef,
-    pub filter_type: PyClassRef,
-    pub float_type: PyClassRef,
-    pub frame_type: PyClassRef,
-    pub frozenset_type: PyClassRef,
-    pub generator_type: PyClassRef,
-    pub int_type: PyClassRef,
-    pub iter_type: PyClassRef,
-    pub complex_type: PyClassRef,
     pub true_value: PyIntRef,
     pub false_value: PyIntRef,
-    pub list_type: PyClassRef,
-    pub listiterator_type: PyClassRef,
-    pub listreverseiterator_type: PyClassRef,
-    pub striterator_type: PyClassRef,
-    pub strreverseiterator_type: PyClassRef,
-    pub dictkeyiterator_type: PyClassRef,
-    pub dictvalueiterator_type: PyClassRef,
-    pub dictitemiterator_type: PyClassRef,
-    pub dictkeys_type: PyClassRef,
-    pub dictvalues_type: PyClassRef,
-    pub dictitems_type: PyClassRef,
-    pub map_type: PyClassRef,
-    pub memoryview_type: PyClassRef,
     pub none: PyNoneRef,
+    pub empty_tuple: PyTupleRef,
+    pub ellipsis_type: PyClassRef,
     pub ellipsis: PyEllipsisRef,
     pub not_implemented: PyNotImplementedRef,
-    pub empty_tuple: PyTupleRef,
-    pub tuple_type: PyClassRef,
-    pub tupleiterator_type: PyClassRef,
-    pub set_type: PyClassRef,
-    pub staticmethod_type: PyClassRef,
-    pub super_type: PyClassRef,
-    pub str_type: PyClassRef,
-    pub range_type: PyClassRef,
-    pub rangeiterator_type: PyClassRef,
-    pub slice_type: PyClassRef,
-    pub type_type: PyClassRef,
-    pub zip_type: PyClassRef,
-    pub function_type: PyClassRef,
-    pub builtin_function_or_method_type: PyClassRef,
-    pub property_type: PyClassRef,
-    pub readonly_property_type: PyClassRef,
-    pub module_type: PyClassRef,
-    pub namespace_type: PyClassRef,
-    pub bound_method_type: PyClassRef,
-    pub weakref_type: PyClassRef,
-    pub weakproxy_type: PyClassRef,
-    pub mappingproxy_type: PyClassRef,
-    pub object: PyClassRef,
-    pub exceptions: exceptions::ExceptionZoo,
-}
 
-pub fn create_type(name: &str, type_type: &PyClassRef, base: &PyClassRef) -> PyClassRef {
-    let dict = PyAttributes::new();
-    objtype::new(type_type.clone(), name, vec![base.clone()], dict).unwrap()
+    pub types: TypeZoo,
+    pub exceptions: exceptions::ExceptionZoo,
 }
 
 pub type PyNotImplementedRef = PyRef<PyNotImplemented>;
@@ -201,115 +127,12 @@ impl PyValue for PyEllipsis {
     }
 }
 
-fn init_type_hierarchy() -> (PyClassRef, PyClassRef) {
-    // `type` inherits from `object`
-    // and both `type` and `object are instances of `type`.
-    // to produce this circular dependency, we need an unsafe block.
-    // (and yes, this will never get dropped. TODO?)
-    let (type_type, object_type) = unsafe {
-        let object_type = PyObject {
-            typ: mem::uninitialized(), // !
-            dict: None,
-            payload: PyClass {
-                name: String::from("object"),
-                mro: vec![],
-                subclasses: RefCell::new(vec![]),
-                attributes: RefCell::new(PyAttributes::new()),
-            },
-        }
-        .into_ref();
-
-        let type_type = PyObject {
-            typ: mem::uninitialized(), // !
-            dict: None,
-            payload: PyClass {
-                name: String::from("type"),
-                mro: vec![object_type.clone().downcast().unwrap()],
-                subclasses: RefCell::new(vec![]),
-                attributes: RefCell::new(PyAttributes::new()),
-            },
-        }
-        .into_ref();
-
-        let object_type_ptr = PyObjectRef::into_raw(object_type.clone()) as *mut PyObject<PyClass>;
-        let type_type_ptr = PyObjectRef::into_raw(type_type.clone()) as *mut PyObject<PyClass>;
-
-        let type_type: PyClassRef = type_type.downcast().unwrap();
-        let object_type: PyClassRef = object_type.downcast().unwrap();
-
-        ptr::write(&mut (*object_type_ptr).typ, type_type.clone());
-        ptr::write(&mut (*type_type_ptr).typ, type_type.clone());
-
-        (type_type, object_type)
-    };
-
-    object_type
-        .subclasses
-        .borrow_mut()
-        .push(objweakref::PyWeak::downgrade(&type_type.as_object()));
-
-    (type_type, object_type)
-}
-
 // Basic objects:
 impl PyContext {
     pub fn new() -> Self {
         flame_guard!("init PyContext");
-        let (type_type, object_type) = init_type_hierarchy();
-
-        let dict_type = create_type("dict", &type_type, &object_type);
-        let module_type = create_type("module", &type_type, &object_type);
-        let namespace_type = create_type("SimpleNamespace", &type_type, &object_type);
-        let classmethod_type = create_type("classmethod", &type_type, &object_type);
-        let staticmethod_type = create_type("staticmethod", &type_type, &object_type);
-        let function_type = create_type("function", &type_type, &object_type);
-        let builtin_function_or_method_type =
-            create_type("builtin_function_or_method", &type_type, &object_type);
-        let property_type = create_type("property", &type_type, &object_type);
-        let readonly_property_type = create_type("readonly_property", &type_type, &object_type);
-        let super_type = create_type("super", &type_type, &object_type);
-        let weakref_type = create_type("ref", &type_type, &object_type);
-        let weakproxy_type = create_type("weakproxy", &type_type, &object_type);
-        let generator_type = create_type("generator", &type_type, &object_type);
-        let bound_method_type = create_type("method", &type_type, &object_type);
-        let str_type = create_type("str", &type_type, &object_type);
-        let list_type = create_type("list", &type_type, &object_type);
-        let listiterator_type = create_type("list_iterator", &type_type, &object_type);
-        let listreverseiterator_type =
-            create_type("list_reverseiterator", &type_type, &object_type);
-        let striterator_type = create_type("str_iterator", &type_type, &object_type);
-        let strreverseiterator_type = create_type("str_reverseiterator", &type_type, &object_type);
-        let dictkeys_type = create_type("dict_keys", &type_type, &object_type);
-        let dictvalues_type = create_type("dict_values", &type_type, &object_type);
-        let dictitems_type = create_type("dict_items", &type_type, &object_type);
-        let dictkeyiterator_type = create_type("dict_keyiterator", &type_type, &object_type);
-        let dictvalueiterator_type = create_type("dict_valueiterator", &type_type, &object_type);
-        let dictitemiterator_type = create_type("dict_itemiterator", &type_type, &object_type);
-        let set_type = create_type("set", &type_type, &object_type);
-        let frozenset_type = create_type("frozenset", &type_type, &object_type);
-        let int_type = create_type("int", &type_type, &object_type);
-        let float_type = create_type("float", &type_type, &object_type);
-        let frame_type = create_type("frame", &type_type, &object_type);
-        let complex_type = create_type("complex", &type_type, &object_type);
-        let bytes_type = create_type("bytes", &type_type, &object_type);
-        let bytesiterator_type = create_type("bytes_iterator", &type_type, &object_type);
-        let bytearray_type = create_type("bytearray", &type_type, &object_type);
-        let bytearrayiterator_type = create_type("bytearray_iterator", &type_type, &object_type);
-        let tuple_type = create_type("tuple", &type_type, &object_type);
-        let tupleiterator_type = create_type("tuple_iterator", &type_type, &object_type);
-        let iter_type = create_type("iter", &type_type, &object_type);
-        let enumerate_type = create_type("enumerate", &type_type, &object_type);
-        let filter_type = create_type("filter", &type_type, &object_type);
-        let map_type = create_type("map", &type_type, &object_type);
-        let zip_type = create_type("zip", &type_type, &object_type);
-        let bool_type = create_type("bool", &type_type, &int_type);
-        let memoryview_type = create_type("memoryview", &type_type, &object_type);
-        let code_type = create_type("code", &type_type, &object_type);
-        let range_type = create_type("range", &type_type, &object_type);
-        let rangeiterator_type = create_type("range_iterator", &type_type, &object_type);
-        let slice_type = create_type("slice", &type_type, &object_type);
-        let mappingproxy_type = create_type("mappingproxy", &type_type, &object_type);
-        let exceptions = exceptions::ExceptionZoo::new(&type_type, &object_type);
+        let types = TypeZoo::new();
+        let exceptions = exceptions::ExceptionZoo::new(&types.type_type, &types.object_type);
 
         fn create_object<T: PyObjectPayload>(payload: T, cls: &PyClassRef) -> PyRef<T> {
             PyRef {
@@ -318,297 +141,213 @@ impl PyContext {
             }
         }
 
-        let none_type = create_type("NoneType", &type_type, &object_type);
+        let none_type = create_type("NoneType", &types.type_type, &types.object_type);
         let none = create_object(PyNone, &none_type);
 
-        let ellipsis_type = create_type("EllipsisType", &type_type, &object_type);
+        let ellipsis_type = create_type("EllipsisType", &types.type_type, &types.object_type);
         let ellipsis = create_object(PyEllipsis, &ellipsis_type);
 
-        let not_implemented_type = create_type("NotImplementedType", &type_type, &object_type);
+        let not_implemented_type =
+            create_type("NotImplementedType", &types.type_type, &types.object_type);
         let not_implemented = create_object(PyNotImplemented, &not_implemented_type);
 
-        let true_value = create_object(PyInt::new(BigInt::one()), &bool_type);
-        let false_value = create_object(PyInt::new(BigInt::zero()), &bool_type);
+        let true_value = create_object(PyInt::new(BigInt::one()), &types.bool_type);
+        let false_value = create_object(PyInt::new(BigInt::zero()), &types.bool_type);
 
-        let empty_tuple = create_object(PyTuple::from(vec![]), &tuple_type);
+        let empty_tuple = create_object(PyTuple::from(vec![]), &types.tuple_type);
 
         let context = PyContext {
-            bool_type,
-            memoryview_type,
-            bytearray_type,
-            bytearrayiterator_type,
-            bytes_type,
-            bytesiterator_type,
-            code_type,
-            complex_type,
-            classmethod_type,
-            int_type,
-            float_type,
-            frame_type,
-            staticmethod_type,
-            list_type,
-            listiterator_type,
-            listreverseiterator_type,
-            striterator_type,
-            strreverseiterator_type,
-            dictkeys_type,
-            dictvalues_type,
-            dictitems_type,
-            dictkeyiterator_type,
-            dictvalueiterator_type,
-            dictitemiterator_type,
-            set_type,
-            frozenset_type,
             true_value,
             false_value,
-            tuple_type,
-            tupleiterator_type,
-            iter_type,
-            ellipsis_type,
-            enumerate_type,
-            filter_type,
-            map_type,
-            zip_type,
-            dict_type,
+            not_implemented,
             none,
             ellipsis,
-            not_implemented,
-            str_type,
-            range_type,
-            rangeiterator_type,
-            slice_type,
-            object: object_type,
-            function_type,
-            builtin_function_or_method_type,
-            super_type,
-            mappingproxy_type,
-            property_type,
-            readonly_property_type,
-            generator_type,
-            module_type,
-            namespace_type,
-            bound_method_type,
-            weakref_type,
-            weakproxy_type,
-            type_type,
+            ellipsis_type,
+
+            types,
             exceptions,
             empty_tuple,
         };
-        objtype::init(&context);
-        objlist::init(&context);
-        objset::init(&context);
-        objtuple::init(&context);
-        objobject::init(&context);
-        objdict::init(&context);
-        objfunction::init(&context);
-        objstaticmethod::init(&context);
-        objclassmethod::init(&context);
-        objgenerator::init(&context);
-        objint::init(&context);
-        objfloat::init(&context);
-        objcomplex::init(&context);
-        objbytes::init(&context);
-        objbytearray::init(&context);
-        objproperty::init(&context);
-        objmemory::init(&context);
-        objstr::init(&context);
-        objrange::init(&context);
-        objslice::init(&context);
-        objsuper::init(&context);
-        objtuple::init(&context);
-        objiter::init(&context);
-        objellipsis::init(&context);
-        objenumerate::init(&context);
-        objfilter::init(&context);
-        objmap::init(&context);
-        objzip::init(&context);
-        objbool::init(&context);
-        objcode::init(&context);
-        objframe::init(&context);
-        objweakref::init(&context);
-        objweakproxy::init(&context);
-        objnone::init(&context);
-        objmodule::init(&context);
-        objnamespace::init(&context);
-        objmappingproxy::init(&context);
+        initialize_types(&context);
+
         exceptions::init(&context);
         context
     }
 
     pub fn bytearray_type(&self) -> PyClassRef {
-        self.bytearray_type.clone()
+        self.types.bytearray_type.clone()
     }
 
     pub fn bytearrayiterator_type(&self) -> PyClassRef {
-        self.bytearrayiterator_type.clone()
+        self.types.bytearrayiterator_type.clone()
     }
 
     pub fn bytes_type(&self) -> PyClassRef {
-        self.bytes_type.clone()
+        self.types.bytes_type.clone()
     }
 
     pub fn bytesiterator_type(&self) -> PyClassRef {
-        self.bytesiterator_type.clone()
+        self.types.bytesiterator_type.clone()
     }
 
     pub fn code_type(&self) -> PyClassRef {
-        self.code_type.clone()
+        self.types.code_type.clone()
     }
 
     pub fn complex_type(&self) -> PyClassRef {
-        self.complex_type.clone()
+        self.types.complex_type.clone()
     }
 
     pub fn dict_type(&self) -> PyClassRef {
-        self.dict_type.clone()
+        self.types.dict_type.clone()
     }
 
     pub fn float_type(&self) -> PyClassRef {
-        self.float_type.clone()
+        self.types.float_type.clone()
     }
 
     pub fn frame_type(&self) -> PyClassRef {
-        self.frame_type.clone()
+        self.types.frame_type.clone()
     }
 
     pub fn int_type(&self) -> PyClassRef {
-        self.int_type.clone()
+        self.types.int_type.clone()
     }
 
     pub fn list_type(&self) -> PyClassRef {
-        self.list_type.clone()
+        self.types.list_type.clone()
     }
 
     pub fn listiterator_type(&self) -> PyClassRef {
-        self.listiterator_type.clone()
+        self.types.listiterator_type.clone()
     }
 
     pub fn listreverseiterator_type(&self) -> PyClassRef {
-        self.listreverseiterator_type.clone()
+        self.types.listreverseiterator_type.clone()
     }
 
     pub fn striterator_type(&self) -> PyClassRef {
-        self.striterator_type.clone()
+        self.types.striterator_type.clone()
     }
 
     pub fn strreverseiterator_type(&self) -> PyClassRef {
-        self.strreverseiterator_type.clone()
+        self.types.strreverseiterator_type.clone()
     }
 
     pub fn module_type(&self) -> PyClassRef {
-        self.module_type.clone()
+        self.types.module_type.clone()
     }
 
     pub fn namespace_type(&self) -> PyClassRef {
-        self.namespace_type.clone()
+        self.types.namespace_type.clone()
     }
 
     pub fn set_type(&self) -> PyClassRef {
-        self.set_type.clone()
+        self.types.set_type.clone()
     }
 
     pub fn range_type(&self) -> PyClassRef {
-        self.range_type.clone()
+        self.types.range_type.clone()
     }
 
     pub fn rangeiterator_type(&self) -> PyClassRef {
-        self.rangeiterator_type.clone()
+        self.types.rangeiterator_type.clone()
     }
 
     pub fn slice_type(&self) -> PyClassRef {
-        self.slice_type.clone()
+        self.types.slice_type.clone()
     }
 
     pub fn frozenset_type(&self) -> PyClassRef {
-        self.frozenset_type.clone()
+        self.types.frozenset_type.clone()
     }
 
     pub fn bool_type(&self) -> PyClassRef {
-        self.bool_type.clone()
+        self.types.bool_type.clone()
     }
 
     pub fn memoryview_type(&self) -> PyClassRef {
-        self.memoryview_type.clone()
+        self.types.memoryview_type.clone()
     }
 
     pub fn tuple_type(&self) -> PyClassRef {
-        self.tuple_type.clone()
+        self.types.tuple_type.clone()
     }
 
     pub fn tupleiterator_type(&self) -> PyClassRef {
-        self.tupleiterator_type.clone()
+        self.types.tupleiterator_type.clone()
     }
 
     pub fn iter_type(&self) -> PyClassRef {
-        self.iter_type.clone()
+        self.types.iter_type.clone()
     }
 
     pub fn enumerate_type(&self) -> PyClassRef {
-        self.enumerate_type.clone()
+        self.types.enumerate_type.clone()
     }
 
     pub fn filter_type(&self) -> PyClassRef {
-        self.filter_type.clone()
+        self.types.filter_type.clone()
     }
 
     pub fn map_type(&self) -> PyClassRef {
-        self.map_type.clone()
+        self.types.map_type.clone()
     }
 
     pub fn zip_type(&self) -> PyClassRef {
-        self.zip_type.clone()
+        self.types.zip_type.clone()
     }
 
     pub fn str_type(&self) -> PyClassRef {
-        self.str_type.clone()
+        self.types.str_type.clone()
     }
 
     pub fn super_type(&self) -> PyClassRef {
-        self.super_type.clone()
+        self.types.super_type.clone()
     }
 
     pub fn function_type(&self) -> PyClassRef {
-        self.function_type.clone()
+        self.types.function_type.clone()
     }
 
     pub fn builtin_function_or_method_type(&self) -> PyClassRef {
-        self.builtin_function_or_method_type.clone()
+        self.types.builtin_function_or_method_type.clone()
     }
 
     pub fn property_type(&self) -> PyClassRef {
-        self.property_type.clone()
+        self.types.property_type.clone()
     }
 
     pub fn readonly_property_type(&self) -> PyClassRef {
-        self.readonly_property_type.clone()
+        self.types.readonly_property_type.clone()
     }
 
     pub fn classmethod_type(&self) -> PyClassRef {
-        self.classmethod_type.clone()
+        self.types.classmethod_type.clone()
     }
 
     pub fn staticmethod_type(&self) -> PyClassRef {
-        self.staticmethod_type.clone()
+        self.types.staticmethod_type.clone()
     }
 
     pub fn generator_type(&self) -> PyClassRef {
-        self.generator_type.clone()
+        self.types.generator_type.clone()
     }
 
     pub fn bound_method_type(&self) -> PyClassRef {
-        self.bound_method_type.clone()
+        self.types.bound_method_type.clone()
     }
 
     pub fn weakref_type(&self) -> PyClassRef {
-        self.weakref_type.clone()
+        self.types.weakref_type.clone()
     }
 
     pub fn weakproxy_type(&self) -> PyClassRef {
-        self.weakproxy_type.clone()
+        self.types.weakproxy_type.clone()
     }
 
     pub fn type_type(&self) -> PyClassRef {
-        self.type_type.clone()
+        self.types.type_type.clone()
     }
 
     pub fn none(&self) -> PyObjectRef {
@@ -624,7 +363,7 @@ impl PyContext {
     }
 
     pub fn object(&self) -> PyClassRef {
-        self.object.clone()
+        self.types.object_type.clone()
     }
 
     pub fn new_int<T: Into<BigInt>>(&self, i: T) -> PyObjectRef {
@@ -691,16 +430,6 @@ impl PyContext {
         objtype::new(self.type_type(), name, vec![base], PyAttributes::new()).unwrap()
     }
 
-    pub fn new_module(&self, name: &str, dict: PyDictRef) -> PyObjectRef {
-        PyObject::new(
-            PyModule {
-                name: name.to_string(),
-            },
-            self.module_type.clone(),
-            Some(dict),
-        )
-    }
-
     pub fn new_namespace(&self) -> PyObjectRef {
         PyObject::new(PyNamespace, self.namespace_type(), Some(self.new_dict()))
     }
@@ -948,7 +677,7 @@ pub struct PyCallable {
 impl PyCallable {
     #[inline]
     pub fn invoke(&self, args: impl Into<PyFuncArgs>, vm: &VirtualMachine) -> PyResult {
-        vm.invoke(self.obj.clone(), args)
+        vm.invoke(&self.obj, args)
     }
 
     #[inline]
@@ -1103,8 +832,9 @@ impl<T> PyIterable<T> {
     /// This operation may fail if an exception is raised while invoking the
     /// `__iter__` method of the iterable object.
     pub fn iter<'a>(&self, vm: &'a VirtualMachine) -> PyResult<PyIterator<'a, T>> {
+        let method = &self.method;
         let iter_obj = vm.invoke(
-            self.method.clone(),
+            method,
             PyFuncArgs {
                 args: vec![],
                 kwargs: IndexMap::new(),
diff --git a/vm/src/stdlib/ast.rs b/vm/src/stdlib/ast.rs
index 9543d5ce1..19a4e084a 100644
--- a/vm/src/stdlib/ast.rs
+++ b/vm/src/stdlib/ast.rs
@@ -332,11 +332,8 @@ fn expression_to_ast(vm: &VirtualMachine, expression: &ast::Expression) -> PyRes
                 operand => expression_to_ast(vm, a)?,
             })
         }
-        BoolOp { a, op, b } => {
-            // Attach values:
-            let py_a = expression_to_ast(vm, a)?.into_object();
-            let py_b = expression_to_ast(vm, b)?.into_object();
-            let py_values = vm.ctx.new_tuple(vec![py_a, py_b]);
+        BoolOp { op, values } => {
+            let py_values = expressions_to_ast(vm, values)?;
 
             let str_op = match op {
                 ast::BooleanOperator::And => "And",
diff --git a/vm/src/stdlib/errno.rs b/vm/src/stdlib/errno.rs
index 0a8587087..6f82351f2 100644
--- a/vm/src/stdlib/errno.rs
+++ b/vm/src/stdlib/errno.rs
@@ -149,6 +149,96 @@ const ERROR_CODES: &[(&str, i32)] = &[
     ("ERFKILL", libc::ERFKILL),
 ];
 
+#[cfg(all(unix, not(target_os = "linux")))]
+const ERROR_CODES: &[(&str, i32)] = &[
+    ("ENODEV", libc::ENODEV),
+    ("EHOSTUNREACH", libc::EHOSTUNREACH),
+    ("ENOMSG", libc::ENOMSG),
+    ("ENODATA", libc::ENODATA),
+    ("ENOTBLK", libc::ENOTBLK),
+    ("ENOSYS", libc::ENOSYS),
+    ("EPIPE", libc::EPIPE),
+    ("EINVAL", libc::EINVAL),
+    ("EOVERFLOW", libc::EOVERFLOW),
+    ("EINTR", libc::EINTR),
+    ("EUSERS", libc::EUSERS),
+    ("ENOTEMPTY", libc::ENOTEMPTY),
+    ("ENOBUFS", libc::ENOBUFS),
+    ("EPROTO", libc::EPROTO),
+    ("EREMOTE", libc::EREMOTE),
+    ("ECHILD", libc::ECHILD),
+    ("ELOOP", libc::ELOOP),
+    ("EXDEV", libc::EXDEV),
+    ("E2BIG", libc::E2BIG),
+    ("ESRCH", libc::ESRCH),
+    ("EMSGSIZE", libc::EMSGSIZE),
+    ("EAFNOSUPPORT", libc::EAFNOSUPPORT),
+    ("EHOSTDOWN", libc::EHOSTDOWN),
+    ("EPFNOSUPPORT", libc::EPFNOSUPPORT),
+    ("ENOPROTOOPT", libc::ENOPROTOOPT),
+    ("EBUSY", libc::EBUSY),
+    ("EAGAIN", libc::EAGAIN),
+    ("EISCONN", libc::EISCONN),
+    ("ESHUTDOWN", libc::ESHUTDOWN),
+    ("EBADF", libc::EBADF),
+    ("EMULTIHOP", libc::EMULTIHOP),
+    ("EIO", libc::EIO),
+    ("EPROTOTYPE", libc::EPROTOTYPE),
+    ("ENOSPC", libc::ENOSPC),
+    ("ENOEXEC", libc::ENOEXEC),
+    ("EALREADY", libc::EALREADY),
+    ("ENETDOWN", libc::ENETDOWN),
+    ("EACCES", libc::EACCES),
+    ("EILSEQ", libc::EILSEQ),
+    ("ENOTDIR", libc::ENOTDIR),
+    ("EPERM", libc::EPERM),
+    ("EDOM", libc::EDOM),
+    ("ECONNREFUSED", libc::ECONNREFUSED),
+    ("EISDIR", libc::EISDIR),
+    ("EPROTONOSUPPORT", libc::EPROTONOSUPPORT),
+    ("EROFS", libc::EROFS),
+    ("EADDRNOTAVAIL", libc::EADDRNOTAVAIL),
+    ("EIDRM", libc::EIDRM),
+    ("EBADMSG", libc::EBADMSG),
+    ("ENFILE", libc::ENFILE),
+    ("ESPIPE", libc::ESPIPE),
+    ("ENOLINK", libc::ENOLINK),
+    ("ENETRESET", libc::ENETRESET),
+    ("ETIMEDOUT", libc::ETIMEDOUT),
+    ("ENOENT", libc::ENOENT),
+    ("EEXIST", libc::EEXIST),
+    ("EDQUOT", libc::EDQUOT),
+    ("ENOSTR", libc::ENOSTR),
+    ("EFAULT", libc::EFAULT),
+    ("EFBIG", libc::EFBIG),
+    ("ENOTCONN", libc::ENOTCONN),
+    ("EDESTADDRREQ", libc::EDESTADDRREQ),
+    ("ENOLCK", libc::ENOLCK),
+    ("ECONNABORTED", libc::ECONNABORTED),
+    ("ENETUNREACH", libc::ENETUNREACH),
+    ("ESTALE", libc::ESTALE),
+    ("ENOSR", libc::ENOSR),
+    ("ENOMEM", libc::ENOMEM),
+    ("ENOTSOCK", libc::ENOTSOCK),
+    ("EMLINK", libc::EMLINK),
+    ("ERANGE", libc::ERANGE),
+    ("ECONNRESET", libc::ECONNRESET),
+    ("EADDRINUSE", libc::EADDRINUSE),
+    ("ENOTSUP", libc::ENOTSUP),
+    ("ENAMETOOLONG", libc::ENAMETOOLONG),
+    ("ENOTTY", libc::ENOTTY),
+    ("ESOCKTNOSUPPORT", libc::ESOCKTNOSUPPORT),
+    ("ETIME", libc::ETIME),
+    ("ETOOMANYREFS", libc::ETOOMANYREFS),
+    ("EMFILE", libc::EMFILE),
+    ("ETXTBSY", libc::ETXTBSY),
+    ("EINPROGRESS", libc::EINPROGRESS),
+    ("ENXIO", libc::ENXIO),
+    ("ECANCELED", libc::ECANCELED),
+    ("EOWNERDEAD", libc::EOWNERDEAD),
+    ("ENOTRECOVERABLE", libc::ENOTRECOVERABLE),
+];
+
 #[cfg(windows)]
 const ERROR_CODES: &[(&str, i32)] = &[
     ("ENODEV", 19),
@@ -254,5 +344,5 @@ const ERROR_CODES: &[(&str, i32)] = &[
     ("ENOTSUP", 129),
 ];
 
-#[cfg(not(any(target_os = "linux", windows)))]
+#[cfg(not(any(unix, windows)))]
 const ERROR_CODES: &[(&str, i32)] = &[];
diff --git a/vm/src/stdlib/functools.rs b/vm/src/stdlib/functools.rs
new file mode 100644
index 000000000..a35bede73
--- /dev/null
+++ b/vm/src/stdlib/functools.rs
@@ -0,0 +1,46 @@
+use crate::function::OptionalArg;
+use crate::obj::objiter;
+use crate::obj::objtype;
+use crate::pyobject::{PyObjectRef, PyResult};
+use crate::vm::VirtualMachine;
+
+pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
+    let ctx = &vm.ctx;
+
+    py_module!(vm, "_functools", {
+        "reduce" => ctx.new_rustfunc(functools_reduce),
+    })
+}
+
+fn functools_reduce(
+    function: PyObjectRef,
+    sequence: PyObjectRef,
+    start_value: OptionalArg<PyObjectRef>,
+    vm: &VirtualMachine,
+) -> PyResult {
+    let iterator = objiter::get_iter(vm, &sequence)?;
+
+    let start_value = if let OptionalArg::Present(val) = start_value {
+        val
+    } else {
+        objiter::call_next(vm, &iterator).map_err(|err| {
+            if objtype::isinstance(&err, &vm.ctx.exceptions.stop_iteration) {
+                let exc_type = vm.ctx.exceptions.type_error.clone();
+                vm.new_exception(
+                    exc_type,
+                    "reduce() of empty sequence with no initial value".to_string(),
+                )
+            } else {
+                err
+            }
+        })?
+    };
+
+    let mut accumulator = start_value;
+
+    while let Ok(next_obj) = objiter::call_next(vm, &iterator) {
+        accumulator = vm.invoke(&function, vec![accumulator, next_obj])?
+    }
+
+    Ok(accumulator)
+}
diff --git a/vm/src/stdlib/io.rs b/vm/src/stdlib/io.rs
index 1bbb4fbae..d7e295b5a 100644
--- a/vm/src/stdlib/io.rs
+++ b/vm/src/stdlib/io.rs
@@ -346,18 +346,36 @@ fn file_io_init(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
 }
 
 fn file_io_read(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
-    arg_check!(vm, args, required = [(file_io, None)]);
+    arg_check!(
+        vm,
+        args,
+        required = [(file_io, None)],
+        optional = [(read_byte, Some(vm.ctx.int_type()))]
+    );
 
     let file_no = vm.get_attribute(file_io.clone(), "fileno")?;
     let raw_fd = objint::get_value(&file_no).to_i64().unwrap();
 
     let mut handle = os::rust_file(raw_fd);
 
-    let mut bytes = vec![];
-    match handle.read_to_end(&mut bytes) {
-        Ok(_) => {}
-        Err(_) => return Err(vm.new_value_error("Error reading from Buffer".to_string())),
-    }
+    let bytes = match read_byte {
+        None => {
+            let mut bytes = vec![];
+            handle
+                .read_to_end(&mut bytes)
+                .map_err(|_| vm.new_value_error("Error reading from Buffer".to_string()))?;
+            bytes
+        }
+        Some(read_byte) => {
+            let mut bytes = vec![0; objint::get_value(&read_byte).to_usize().unwrap()];
+            handle
+                .read_exact(&mut bytes)
+                .map_err(|_| vm.new_value_error("Error reading from Buffer".to_string()))?;
+            let updated = os::raw_file_number(handle);
+            vm.set_attr(file_io, "fileno", vm.ctx.new_int(updated))?;
+            bytes
+        }
+    };
 
     Ok(vm.ctx.new_bytes(bytes))
 }
@@ -431,6 +449,31 @@ fn file_io_write(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
     }
 }
 
+#[cfg(windows)]
+fn file_io_close(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
+    use std::os::windows::io::IntoRawHandle;
+    arg_check!(vm, args, required = [(file_io, None)]);
+    let file_no = vm.get_attribute(file_io.clone(), "fileno")?;
+    let raw_fd = objint::get_value(&file_no).to_i64().unwrap();
+    let handle = os::rust_file(raw_fd);
+    let raw_handle = handle.into_raw_handle();
+    unsafe {
+        kernel32::CloseHandle(raw_handle);
+    }
+    Ok(vm.ctx.none())
+}
+
+#[cfg(unix)]
+fn file_io_close(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
+    arg_check!(vm, args, required = [(file_io, None)]);
+    let file_no = vm.get_attribute(file_io.clone(), "fileno")?;
+    let raw_fd = objint::get_value(&file_no).to_i32().unwrap();
+    unsafe {
+        libc::close(raw_fd);
+    }
+    Ok(vm.ctx.none())
+}
+
 fn file_io_seekable(vm: &VirtualMachine, _args: PyFuncArgs) -> PyResult {
     Ok(vm.ctx.new_bool(true))
 }
@@ -607,7 +650,7 @@ pub fn io_open(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
     // This is subsequently consumed by a Buffered Class.
     let file_io_class = vm.get_attribute(io_module.clone(), "FileIO").unwrap();
     let file_io_obj = vm.invoke(
-        file_io_class,
+        &file_io_class,
         vec![file.clone(), vm.ctx.new_str(mode.clone())],
     )?;
 
@@ -620,13 +663,13 @@ pub fn io_open(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
             let buffered_writer_class = vm
                 .get_attribute(io_module.clone(), "BufferedWriter")
                 .unwrap();
-            vm.invoke(buffered_writer_class, vec![file_io_obj.clone()])
+            vm.invoke(&buffered_writer_class, vec![file_io_obj.clone()])
         }
         'r' => {
             let buffered_reader_class = vm
                 .get_attribute(io_module.clone(), "BufferedReader")
                 .unwrap();
-            vm.invoke(buffered_reader_class, vec![file_io_obj.clone()])
+            vm.invoke(&buffered_reader_class, vec![file_io_obj.clone()])
         }
         //TODO: updating => PyBufferedRandom
         _ => unimplemented!("'a' mode is not yet implemented"),
@@ -637,7 +680,7 @@ pub fn io_open(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
         // a TextIOWrapper which is subsequently returned.
         't' => {
             let text_io_wrapper_class = vm.get_attribute(io_module, "TextIOWrapper").unwrap();
-            vm.invoke(text_io_wrapper_class, vec![buffered.unwrap()])
+            vm.invoke(&text_io_wrapper_class, vec![buffered.unwrap()])
         }
         // If the mode is binary this Buffered class is returned directly at
         // this point.
@@ -678,6 +721,7 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
         "read" => ctx.new_rustfunc(file_io_read),
         "readinto" => ctx.new_rustfunc(file_io_readinto),
         "write" => ctx.new_rustfunc(file_io_write),
+        "close" => ctx.new_rustfunc(file_io_close),
         "seekable" => ctx.new_rustfunc(file_io_seekable)
     });
 
@@ -739,6 +783,7 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
         "TextIOWrapper" => text_io_wrapper,
         "StringIO" => string_io,
         "BytesIO" => bytes_io,
+        "DEFAULT_BUFFER_SIZE" => ctx.new_int(8 * 1024),
     })
 }
 
diff --git a/vm/src/stdlib/itertools.rs b/vm/src/stdlib/itertools.rs
index 732020480..6039c178a 100644
--- a/vm/src/stdlib/itertools.rs
+++ b/vm/src/stdlib/itertools.rs
@@ -218,8 +218,9 @@ impl PyItertoolsStarmap {
     #[pymethod(name = "__next__")]
     fn next(&self, vm: &VirtualMachine) -> PyResult {
         let obj = call_next(vm, &self.iter)?;
+        let function = &self.function;
 
-        vm.invoke(self.function.clone(), vm.extract_elements(&obj)?)
+        vm.invoke(function, vm.extract_elements(&obj)?)
     }
 
     #[pymethod(name = "__iter__")]
@@ -271,8 +272,9 @@ impl PyItertoolsTakewhile {
 
         // might be StopIteration or anything else, which is propaged upwwards
         let obj = call_next(vm, &self.iterable)?;
+        let predicate = &self.predicate;
 
-        let verdict = vm.invoke(self.predicate.clone(), vec![obj.clone()])?;
+        let verdict = vm.invoke(predicate, vec![obj.clone()])?;
         let verdict = objbool::boolval(vm, verdict)?;
         if verdict {
             Ok(obj)
diff --git a/vm/src/stdlib/json.rs b/vm/src/stdlib/json.rs
index 8b5d21b75..aa3fb8157 100644
--- a/vm/src/stdlib/json.rs
+++ b/vm/src/stdlib/json.rs
@@ -1,6 +1,7 @@
 use crate::obj::objstr::PyStringRef;
 use crate::py_serde;
-use crate::pyobject::{create_type, ItemProtocol, PyObjectRef, PyResult};
+use crate::pyobject::{ItemProtocol, PyObjectRef, PyResult};
+use crate::types::create_type;
 use crate::VirtualMachine;
 use serde_json;
 
@@ -10,6 +11,12 @@ pub fn json_dumps(obj: PyObjectRef, vm: &VirtualMachine) -> PyResult<String> {
     serde_json::to_string(&serializer).map_err(|err| vm.new_type_error(err.to_string()))
 }
 
+pub fn json_dump(obj: PyObjectRef, fs: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+    let result = json_dumps(obj, vm)?;
+    vm.call_method(&fs, "write", vec![vm.new_str(result)])?;
+    Ok(vm.get_none())
+}
+
 /// Implement json.loads
 pub fn json_loads(string: PyStringRef, vm: &VirtualMachine) -> PyResult {
     // TODO: Implement non-trivial deserialization case
@@ -33,19 +40,26 @@ pub fn json_loads(string: PyStringRef, vm: &VirtualMachine) -> PyResult {
     })
 }
 
+pub fn json_load(fp: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+    let result = vm.call_method(&fp, "read", vec![])?;
+    json_loads(result.downcast()?, vm)
+}
+
 pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
     let ctx = &vm.ctx;
 
     // TODO: Make this a proper type with a constructor
     let json_decode_error = create_type(
         "JSONDecodeError",
-        &ctx.type_type,
+        &ctx.types.type_type,
         &ctx.exceptions.exception_type,
     );
 
     py_module!(vm, "json", {
         "dumps" => ctx.new_rustfunc(json_dumps),
+        "dump" => ctx.new_rustfunc(json_dump),
         "loads" => ctx.new_rustfunc(json_loads),
+        "load" => ctx.new_rustfunc(json_load),
         "JSONDecodeError" => json_decode_error
     })
 }
diff --git a/vm/src/stdlib/marshal.rs b/vm/src/stdlib/marshal.rs
index e7afc86d2..86f542ff6 100644
--- a/vm/src/stdlib/marshal.rs
+++ b/vm/src/stdlib/marshal.rs
@@ -1,17 +1,17 @@
 use crate::bytecode;
 use crate::obj::objbytes::{PyBytes, PyBytesRef};
 use crate::obj::objcode::{PyCode, PyCodeRef};
-use crate::pyobject::{IntoPyObject, PyObjectRef, PyResult};
+use crate::pyobject::{PyObjectRef, PyResult};
 use crate::vm::VirtualMachine;
 
-fn marshal_dumps(co: PyCodeRef, vm: &VirtualMachine) -> PyResult {
-    PyBytes::new(bincode::serialize(&co.code).unwrap()).into_pyobject(vm)
+fn marshal_dumps(co: PyCodeRef, _vm: &VirtualMachine) -> PyBytes {
+    PyBytes::new(bincode::serialize(&co.code).unwrap())
 }
 
-fn marshal_loads(code_bytes: PyBytesRef, vm: &VirtualMachine) -> PyResult {
-    let code = bincode::deserialize::<bytecode::CodeObject>(&code_bytes).unwrap();
-    let pycode = PyCode { code };
-    pycode.into_pyobject(vm)
+fn marshal_loads(code_bytes: PyBytesRef, vm: &VirtualMachine) -> PyResult<PyCode> {
+    let code = bincode::deserialize::<bytecode::CodeObject>(&code_bytes)
+        .map_err(|_| vm.new_value_error("Couldn't deserialize python bytecode".to_owned()))?;
+    Ok(PyCode { code })
 }
 
 pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
@@ -19,6 +19,6 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
 
     py_module!(vm, "marshal", {
         "loads" => ctx.new_rustfunc(marshal_loads),
-        "dumps" => ctx.new_rustfunc(marshal_dumps)
+        "dumps" => ctx.new_rustfunc(marshal_dumps),
     })
 }
diff --git a/vm/src/stdlib/math.rs b/vm/src/stdlib/math.rs
index 36dad8bca..1627f6bbb 100644
--- a/vm/src/stdlib/math.rs
+++ b/vm/src/stdlib/math.rs
@@ -6,9 +6,14 @@
 use statrs::function::erf::{erf, erfc};
 use statrs::function::gamma::{gamma, ln_gamma};
 
+use num_bigint::BigInt;
+use num_traits::cast::ToPrimitive;
+use num_traits::{One, Zero};
+
 use crate::function::PyFuncArgs;
+use crate::obj::objfloat::PyFloatRef;
 use crate::obj::objint::PyIntRef;
-use crate::obj::{objfloat, objtype};
+use crate::obj::{objfloat, objint, objtype};
 use crate::pyobject::{PyObjectRef, PyResult, TypeProtocol};
 use crate::vm::VirtualMachine;
 
@@ -181,7 +186,7 @@ fn try_magic_method(func_name: &str, vm: &VirtualMachine, value: &PyObjectRef) -
             func_name,
         )
     })?;
-    vm.invoke(method, vec![])
+    vm.invoke(&method, vec![])
 }
 
 fn math_trunc(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
@@ -191,7 +196,7 @@ fn math_trunc(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
 
 fn math_ceil(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
     arg_check!(vm, args, required = [(value, None)]);
-    if objtype::isinstance(value, &vm.ctx.float_type) {
+    if objtype::isinstance(value, &vm.ctx.float_type()) {
         let v = objfloat::get_value(value);
         Ok(vm.ctx.new_float(v.ceil()))
     } else {
@@ -201,7 +206,7 @@ fn math_ceil(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
 
 fn math_floor(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
     arg_check!(vm, args, required = [(value, None)]);
-    if objtype::isinstance(value, &vm.ctx.float_type) {
+    if objtype::isinstance(value, &vm.ctx.float_type()) {
         let v = objfloat::get_value(value);
         Ok(vm.ctx.new_float(v.floor()))
     } else {
@@ -226,11 +231,29 @@ fn math_frexp(value: PyObjectRef, vm: &VirtualMachine) -> PyResult {
     )
 }
 
+fn math_ldexp(value: PyFloatRef, i: PyIntRef, vm: &VirtualMachine) -> PyResult {
+    Ok(vm
+        .ctx
+        .new_float(value.to_f64() * (2_f64).powf(i.as_bigint().to_f64().unwrap())))
+}
+
 fn math_gcd(a: PyIntRef, b: PyIntRef, vm: &VirtualMachine) -> PyResult {
     use num_integer::Integer;
     Ok(vm.new_int(a.as_bigint().gcd(b.as_bigint())))
 }
 
+fn math_factorial(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
+    arg_check!(vm, args, required = [(value, None)]);
+    let value = objint::get_value(value);
+    if *value < BigInt::zero() {
+        return Err(vm.new_value_error("factorial() not defined for negative values".to_string()));
+    } else if *value <= BigInt::one() {
+        return Ok(vm.ctx.new_int(BigInt::from(1u64)));
+    }
+    let ret: BigInt = num_iter::range_inclusive(BigInt::from(1u64), value.clone()).product();
+    Ok(vm.ctx.new_int(ret))
+}
+
 pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
     let ctx = &vm.ctx;
 
@@ -279,6 +302,7 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
         "lgamma" => ctx.new_rustfunc(math_lgamma),
 
         "frexp" => ctx.new_rustfunc(math_frexp),
+        "ldexp" => ctx.new_rustfunc(math_ldexp),
 
         // Rounding functions:
         "trunc" => ctx.new_rustfunc(math_trunc),
@@ -288,6 +312,9 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
         // Gcd function
         "gcd" => ctx.new_rustfunc(math_gcd),
 
+        // Factorial function
+        "factorial" => ctx.new_rustfunc(math_factorial),
+
         // Constants:
         "pi" => ctx.new_float(std::f64::consts::PI), // 3.14159...
         "e" => ctx.new_float(std::f64::consts::E), // 2.71..
diff --git a/vm/src/stdlib/mod.rs b/vm/src/stdlib/mod.rs
index 0ec7643c5..076274dc3 100644
--- a/vm/src/stdlib/mod.rs
+++ b/vm/src/stdlib/mod.rs
@@ -5,6 +5,7 @@ mod codecs;
 mod collections;
 mod dis;
 mod errno;
+mod functools;
 mod hashlib;
 mod imp;
 mod itertools;
@@ -43,6 +44,8 @@ mod pwd;
 pub mod signal;
 #[cfg(not(target_arch = "wasm32"))]
 mod subprocess;
+#[cfg(not(target_arch = "wasm32"))]
+mod zlib;
 
 use crate::pyobject::PyObjectRef;
 
@@ -55,6 +58,7 @@ pub fn get_module_inits() -> HashMap<String, StdlibInitFunc> {
         "dis".to_string() => Box::new(dis::make_module),
         "_codecs".to_string() => Box::new(codecs::make_module),
         "_collections".to_string() => Box::new(collections::make_module),
+        "_functools".to_string() => Box::new(functools::make_module),
         "errno".to_string() => Box::new(errno::make_module),
         "hashlib".to_string() => Box::new(hashlib::make_module),
         "itertools".to_string() => Box::new(itertools::make_module),
@@ -99,6 +103,7 @@ pub fn get_module_inits() -> HashMap<String, StdlibInitFunc> {
         modules.insert("socket".to_string(), Box::new(socket::make_module));
         modules.insert("signal".to_string(), Box::new(signal::make_module));
         modules.insert("subprocess".to_string(), Box::new(subprocess::make_module));
+        modules.insert("zlib".to_string(), Box::new(zlib::make_module));
     }
 
     // Unix-only
diff --git a/vm/src/stdlib/os.rs b/vm/src/stdlib/os.rs
index b010c401c..f0550d587 100644
--- a/vm/src/stdlib/os.rs
+++ b/vm/src/stdlib/os.rs
@@ -1,3 +1,4 @@
+use num_cpus;
 use std::cell::RefCell;
 use std::ffi::CStr;
 use std::fs::File;
@@ -10,7 +11,7 @@ use std::{env, fs};
 
 #[cfg(unix)]
 use nix::errno::Errno;
-#[cfg(unix)]
+#[cfg(all(unix, not(target_os = "redox")))]
 use nix::pty::openpty;
 #[cfg(unix)]
 use nix::unistd::{self, Gid, Pid, Uid};
@@ -125,7 +126,7 @@ pub fn os_open(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
     Ok(vm.ctx.new_int(raw_file_number(handle)))
 }
 
-fn convert_io_error(vm: &VirtualMachine, err: io::Error) -> PyObjectRef {
+pub fn convert_io_error(vm: &VirtualMachine, err: io::Error) -> PyObjectRef {
     let os_error = match err.kind() {
         ErrorKind::NotFound => {
             let exc_type = vm.ctx.exceptions.file_not_found_error.clone();
@@ -185,6 +186,95 @@ fn convert_nix_errno(vm: &VirtualMachine, errno: Errno) -> PyClassRef {
     }
 }
 
+// Flags for os_access
+bitflags! {
+    pub struct AccessFlags: u8{
+        const F_OK = 0;
+        const R_OK = 4;
+        const W_OK = 2;
+        const X_OK = 1;
+    }
+}
+
+#[cfg(unix)]
+struct Permissions {
+    is_readable: bool,
+    is_writable: bool,
+    is_executable: bool,
+}
+
+#[cfg(unix)]
+fn get_permissions(mode: u32) -> Permissions {
+    Permissions {
+        is_readable: mode & 4 != 0,
+        is_writable: mode & 2 != 0,
+        is_executable: mode & 1 != 0,
+    }
+}
+
+#[cfg(unix)]
+fn get_right_permission(
+    mode: u32,
+    file_owner: Uid,
+    file_group: Gid,
+) -> Result<Permissions, nix::Error> {
+    let owner_mode = (mode & 0o700) >> 6;
+    let owner_permissions = get_permissions(owner_mode);
+
+    let group_mode = (mode & 0o070) >> 3;
+    let group_permissions = get_permissions(group_mode);
+
+    let others_mode = mode & 0o007;
+    let others_permissions = get_permissions(others_mode);
+
+    let user_id = nix::unistd::getuid();
+    let groups_ids = nix::unistd::getgroups()?;
+
+    if file_owner == user_id {
+        Ok(owner_permissions)
+    } else if groups_ids.contains(&file_group) {
+        Ok(group_permissions)
+    } else {
+        Ok(others_permissions)
+    }
+}
+
+#[cfg(unix)]
+fn os_access(path: PyStringRef, mode: u8, vm: &VirtualMachine) -> PyResult<bool> {
+    use std::os::unix::fs::MetadataExt;
+
+    let path = path.as_str();
+
+    let flags = AccessFlags::from_bits(mode).ok_or_else(|| {
+        vm.new_value_error(
+            "One of the flags is wrong, there are only 4 possibilities F_OK, R_OK, W_OK and X_OK"
+                .to_string(),
+        )
+    })?;
+
+    let metadata = fs::metadata(path);
+
+    // if it's only checking for F_OK
+    if flags == AccessFlags::F_OK {
+        return Ok(metadata.is_ok());
+    }
+
+    let metadata = metadata.map_err(|err| convert_io_error(vm, err))?;
+
+    let user_id = metadata.uid();
+    let group_id = metadata.gid();
+    let mode = metadata.mode();
+
+    let perm = get_right_permission(mode, Uid::from_raw(user_id), Gid::from_raw(group_id))
+        .map_err(|err| convert_nix_error(vm, err))?;
+
+    let r_ok = !flags.contains(AccessFlags::R_OK) || perm.is_readable;
+    let w_ok = !flags.contains(AccessFlags::W_OK) || perm.is_writable;
+    let x_ok = !flags.contains(AccessFlags::X_OK) || perm.is_executable;
+
+    Ok(r_ok && w_ok && x_ok)
+}
+
 fn os_error(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
     arg_check!(
         vm,
@@ -280,6 +370,15 @@ fn _os_environ(vm: &VirtualMachine) -> PyDictRef {
     environ
 }
 
+fn os_readlink(path: PyStringRef, dir_fd: DirFd, vm: &VirtualMachine) -> PyResult {
+    let path = make_path(vm, path, &dir_fd);
+    let path = fs::read_link(path.as_str()).map_err(|err| convert_io_error(vm, err))?;
+    let path = path.into_os_string().into_string().map_err(|_osstr| {
+        vm.new_unicode_decode_error("Can't convert OS path to valid UTF-8 string".into())
+    })?;
+    Ok(vm.ctx.new_str(path))
+}
+
 #[derive(Debug)]
 struct DirEntry {
     entry: fs::DirEntry,
@@ -725,6 +824,11 @@ fn os_getpid(vm: &VirtualMachine) -> PyObjectRef {
     vm.new_int(pid)
 }
 
+fn os_cpu_count(vm: &VirtualMachine) -> PyObjectRef {
+    let cpu_count = num_cpus::get();
+    vm.new_int(cpu_count)
+}
+
 #[cfg(unix)]
 fn os_getppid(vm: &VirtualMachine) -> PyObjectRef {
     let ppid = unistd::getppid().as_raw();
@@ -819,7 +923,7 @@ fn os_seteuid(euid: PyIntRef, vm: &VirtualMachine) -> PyResult<()> {
     unistd::seteuid(Uid::from_raw(euid)).map_err(|err| convert_nix_error(vm, err))
 }
 
-#[cfg(unix)]
+#[cfg(all(unix, not(target_os = "redox")))]
 pub fn os_openpty(vm: &VirtualMachine) -> PyResult {
     match openpty(None, None) {
         Ok(r) => Ok(vm
@@ -923,7 +1027,7 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
         // mkfifo Some Some None
         // mknod Some Some None
         // pathconf Some None None
-        // readlink Some Some None
+        SupportFunc::new(vm, "readlink", os_readlink, Some(false), Some(false), None),
         SupportFunc::new(vm, "remove", os_remove, Some(false), Some(false), None),
         SupportFunc::new(vm, "rename", os_rename, Some(false), Some(false), None),
         SupportFunc::new(vm, "replace", os_rename, Some(false), Some(false), None), // TODO: Fix replace
@@ -957,6 +1061,9 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
         "getcwd" => ctx.new_rustfunc(os_getcwd),
         "chdir" => ctx.new_rustfunc(os_chdir),
         "fspath" => ctx.new_rustfunc(os_fspath),
+         "getpid" => ctx.new_rustfunc(os_getpid),
+        "cpu_count" => ctx.new_rustfunc(os_cpu_count),
+
         "O_RDONLY" => ctx.new_int(libc::O_RDONLY),
         "O_WRONLY" => ctx.new_int(libc::O_WRONLY),
         "O_RDWR" => ctx.new_int(libc::O_RDWR),
@@ -968,7 +1075,6 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
         "R_OK" => ctx.new_int(libc::R_OK),
         "W_OK" => ctx.new_int(libc::W_OK),
         "X_OK" => ctx.new_int(libc::X_OK),
-        "getpid" => ctx.new_rustfunc(os_getpid)
     });
 
     for support in support_funcs {
@@ -1017,6 +1123,8 @@ fn extend_module_platform_specific(vm: &VirtualMachine, module: PyObjectRef) ->
         "setgid" => ctx.new_rustfunc(os_setgid),
         "setpgid" => ctx.new_rustfunc(os_setpgid),
         "setuid" => ctx.new_rustfunc(os_setuid),
+        "access" => ctx.new_rustfunc(os_access),
+
         "O_DSYNC" => ctx.new_int(libc::O_DSYNC),
         "O_RSYNC" => ctx.new_int(libc::O_RSYNC),
         "O_NDELAY" => ctx.new_int(libc::O_NDELAY),
diff --git a/vm/src/stdlib/re.rs b/vm/src/stdlib/re.rs
index b44f5701d..49fba3185 100644
--- a/vm/src/stdlib/re.rs
+++ b/vm/src/stdlib/re.rs
@@ -188,12 +188,18 @@ fn do_findall(vm: &VirtualMachine, pattern: &PyPattern, search_text: PyStringRef
     let out = pattern
         .regex
         .captures_iter(search_text.as_str().as_bytes())
-        .map(|captures| {
-            if captures.len() == 1 {
-                let full = captures.get(1).unwrap().as_bytes();
+        .map(|captures| match captures.len() {
+            1 => {
+                let full = captures.get(0).unwrap().as_bytes();
                 let full = String::from_utf8_lossy(full).into_owned();
                 vm.new_str(full)
-            } else {
+            }
+            2 => {
+                let capture = captures.get(1).unwrap().as_bytes();
+                let capture = String::from_utf8_lossy(capture).into_owned();
+                vm.new_str(capture)
+            }
+            _ => {
                 let out = captures
                     .iter()
                     .skip(1)
@@ -354,6 +360,11 @@ impl PyPattern {
     ) -> PyResult {
         do_split(vm, self, search_text, maxsplit.into_option())
     }
+
+    #[pymethod]
+    fn findall(&self, search_text: PyStringRef, vm: &VirtualMachine) -> PyResult {
+        do_findall(vm, self, search_text)
+    }
 }
 
 #[pyimpl]
diff --git a/vm/src/stdlib/signal.rs b/vm/src/stdlib/signal.rs
index d72085ea0..2950282b1 100644
--- a/vm/src/stdlib/signal.rs
+++ b/vm/src/stdlib/signal.rs
@@ -92,7 +92,7 @@ pub fn check_signals(vm: &VirtualMachine) {
                 .get(&(signum as i32))
                 .expect("Handler should be set")
                 .clone();
-            vm.invoke(handler, vec![vm.new_int(signum), vm.get_none()])
+            vm.invoke(&handler, vec![vm.new_int(signum), vm.get_none()])
                 .expect("Test");
         }
     }
diff --git a/vm/src/stdlib/socket.rs b/vm/src/stdlib/socket.rs
index 22f431a82..c83b75656 100644
--- a/vm/src/stdlib/socket.rs
+++ b/vm/src/stdlib/socket.rs
@@ -4,13 +4,14 @@ use std::io::Read;
 use std::io::Write;
 use std::net::{Ipv4Addr, SocketAddr, TcpListener, TcpStream, ToSocketAddrs, UdpSocket};
 
-#[cfg(unix)]
+#[cfg(all(unix, not(target_os = "redox")))]
 use nix::unistd::sethostname;
 
 use gethostname::gethostname;
 
 use byteorder::{BigEndian, ByteOrder};
 
+use crate::function::PyFuncArgs;
 use crate::obj::objbytes::PyBytesRef;
 use crate::obj::objint::PyIntRef;
 use crate::obj::objstr::PyStringRef;
@@ -21,6 +22,7 @@ use crate::vm::VirtualMachine;
 use crate::obj::objtype::PyClassRef;
 #[cfg(unix)]
 use crate::stdlib::os::convert_nix_error;
+use num_bigint::Sign;
 use num_traits::ToPrimitive;
 
 #[derive(Debug, Copy, Clone)]
@@ -180,6 +182,14 @@ impl SocketRef {
         Socket::new(family, kind).into_ref_with_type(vm, cls)
     }
 
+    fn enter(self, _vm: &VirtualMachine) -> SocketRef {
+        self
+    }
+
+    fn exit(self, _args: PyFuncArgs, _vm: &VirtualMachine) {
+        self.close(_vm)
+    }
+
     fn connect(self, address: Address, vm: &VirtualMachine) -> PyResult<()> {
         let address_string = address.get_address_string();
 
@@ -388,7 +398,7 @@ fn socket_gethostname(vm: &VirtualMachine) -> PyResult {
         .map_err(|err| vm.new_os_error(err.into_string().unwrap()))
 }
 
-#[cfg(unix)]
+#[cfg(all(unix, not(target_os = "redox")))]
 fn socket_sethostname(hostname: PyStringRef, vm: &VirtualMachine) -> PyResult<()> {
     sethostname(hostname.value.as_str()).map_err(|err| convert_nix_error(vm, err))
 }
@@ -409,32 +419,46 @@ fn socket_inet_ntoa(packed_ip: PyBytesRef, vm: &VirtualMachine) -> PyResult {
     Ok(vm.new_str(Ipv4Addr::from(ip_num).to_string()))
 }
 
+fn socket_htonl(host: PyIntRef, vm: &VirtualMachine) -> PyResult {
+    if host.as_bigint().sign() == Sign::Minus {
+        return Err(
+            vm.new_overflow_error("can't convert negative value to unsigned int".to_string())
+        );
+    }
+
+    let host = host.as_bigint().to_u32().unwrap();
+    Ok(vm.new_int(host.to_be()))
+}
+
 pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
     let ctx = &vm.ctx;
 
     let socket = py_class!(ctx, "socket", ctx.object(), {
-         "__new__" => ctx.new_rustfunc(SocketRef::new),
-         "connect" => ctx.new_rustfunc(SocketRef::connect),
-         "recv" => ctx.new_rustfunc(SocketRef::recv),
-         "send" => ctx.new_rustfunc(SocketRef::send),
-         "bind" => ctx.new_rustfunc(SocketRef::bind),
-         "accept" => ctx.new_rustfunc(SocketRef::accept),
-         "listen" => ctx.new_rustfunc(SocketRef::listen),
-         "close" => ctx.new_rustfunc(SocketRef::close),
-         "getsockname" => ctx.new_rustfunc(SocketRef::getsockname),
-         "sendto" => ctx.new_rustfunc(SocketRef::sendto),
-         "recvfrom" => ctx.new_rustfunc(SocketRef::recvfrom),
-         "fileno" => ctx.new_rustfunc(SocketRef::fileno),
+        "__new__" => ctx.new_rustfunc(SocketRef::new),
+        "__enter__" => ctx.new_rustfunc(SocketRef::enter),
+        "__exit__" => ctx.new_rustfunc(SocketRef::exit),
+        "connect" => ctx.new_rustfunc(SocketRef::connect),
+        "recv" => ctx.new_rustfunc(SocketRef::recv),
+        "send" => ctx.new_rustfunc(SocketRef::send),
+        "bind" => ctx.new_rustfunc(SocketRef::bind),
+        "accept" => ctx.new_rustfunc(SocketRef::accept),
+        "listen" => ctx.new_rustfunc(SocketRef::listen),
+        "close" => ctx.new_rustfunc(SocketRef::close),
+        "getsockname" => ctx.new_rustfunc(SocketRef::getsockname),
+        "sendto" => ctx.new_rustfunc(SocketRef::sendto),
+        "recvfrom" => ctx.new_rustfunc(SocketRef::recvfrom),
+        "fileno" => ctx.new_rustfunc(SocketRef::fileno),
     });
 
     let module = py_module!(vm, "socket", {
         "AF_INET" => ctx.new_int(AddressFamily::Inet as i32),
         "SOCK_STREAM" => ctx.new_int(SocketKind::Stream as i32),
-         "SOCK_DGRAM" => ctx.new_int(SocketKind::Dgram as i32),
-         "socket" => socket,
-         "inet_aton" => ctx.new_rustfunc(socket_inet_aton),
-         "inet_ntoa" => ctx.new_rustfunc(socket_inet_ntoa),
-         "gethostname" => ctx.new_rustfunc(socket_gethostname),
+        "SOCK_DGRAM" => ctx.new_int(SocketKind::Dgram as i32),
+        "socket" => socket,
+        "inet_aton" => ctx.new_rustfunc(socket_inet_aton),
+        "inet_ntoa" => ctx.new_rustfunc(socket_inet_ntoa),
+        "gethostname" => ctx.new_rustfunc(socket_gethostname),
+        "htonl" => ctx.new_rustfunc(socket_htonl),
     });
 
     extend_module_platform_specific(vm, module)
@@ -449,8 +473,9 @@ fn extend_module_platform_specific(_vm: &VirtualMachine, module: PyObjectRef) ->
 fn extend_module_platform_specific(vm: &VirtualMachine, module: PyObjectRef) -> PyObjectRef {
     let ctx = &vm.ctx;
 
+    #[cfg(not(target_os = "redox"))]
     extend_module!(vm, module, {
-         "sethostname" => ctx.new_rustfunc(socket_sethostname),
+        "sethostname" => ctx.new_rustfunc(socket_sethostname),
     });
 
     module
diff --git a/vm/src/stdlib/subprocess.rs b/vm/src/stdlib/subprocess.rs
index dd49e247e..3af308f7c 100644
--- a/vm/src/stdlib/subprocess.rs
+++ b/vm/src/stdlib/subprocess.rs
@@ -1,17 +1,19 @@
 use std::cell::RefCell;
+use std::ffi::OsString;
 use std::fs::File;
 use std::time::Duration;
 
 use subprocess;
 
 use crate::function::OptionalArg;
+use crate::obj::objbytes::PyBytesRef;
 use crate::obj::objlist::PyListRef;
 use crate::obj::objsequence;
 use crate::obj::objstr::{self, PyStringRef};
 use crate::obj::objtype::PyClassRef;
 use crate::pyobject::{Either, IntoPyObject, PyObjectRef, PyRef, PyResult, PyValue};
 use crate::stdlib::io::io_open;
-use crate::stdlib::os::{raw_file_number, rust_file};
+use crate::stdlib::os::{convert_io_error, raw_file_number, rust_file};
 use crate::vm::VirtualMachine;
 
 #[derive(Debug)]
@@ -37,6 +39,8 @@ struct PopenArgs {
     stdout: Option<i64>,
     #[pyarg(positional_or_keyword, default = "None")]
     stderr: Option<i64>,
+    #[pyarg(positional_or_keyword, default = "None")]
+    cwd: Option<PyStringRef>,
 }
 
 impl IntoPyObject for subprocess::ExitStatus {
@@ -95,6 +99,7 @@ impl PopenRef {
                 .map(|x| objstr::get_value(x))
                 .collect(),
         };
+        let cwd = args.cwd.map(|x| OsString::from(x.as_str()));
 
         let process = subprocess::Popen::create(
             &command_list,
@@ -102,6 +107,7 @@ impl PopenRef {
                 stdin,
                 stdout,
                 stderr,
+                cwd,
                 ..Default::default()
             },
         )
@@ -149,6 +155,36 @@ impl PopenRef {
     fn stderr(self, vm: &VirtualMachine) -> PyResult {
         convert_to_file_io(&self.process.borrow().stderr, "rb".to_string(), vm)
     }
+
+    fn terminate(self, vm: &VirtualMachine) -> PyResult<()> {
+        self.process
+            .borrow_mut()
+            .terminate()
+            .map_err(|err| convert_io_error(vm, err))
+    }
+
+    fn kill(self, vm: &VirtualMachine) -> PyResult<()> {
+        self.process
+            .borrow_mut()
+            .kill()
+            .map_err(|err| convert_io_error(vm, err))
+    }
+
+    #[allow(clippy::type_complexity)]
+    fn communicate(
+        self,
+        stdin: OptionalArg<PyBytesRef>,
+        vm: &VirtualMachine,
+    ) -> PyResult<(Option<Vec<u8>>, Option<Vec<u8>>)> {
+        self.process
+            .borrow_mut()
+            .communicate_bytes(stdin.into_option().as_ref().map(|bytes| bytes.get_value()))
+            .map_err(|err| convert_io_error(vm, err))
+    }
+
+    fn pid(self, _vm: &VirtualMachine) -> Option<u32> {
+        self.process.borrow().pid()
+    }
 }
 
 pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
@@ -165,6 +201,10 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
         "stdin" => ctx.new_property(PopenRef::stdin),
         "stdout" => ctx.new_property(PopenRef::stdout),
         "stderr" => ctx.new_property(PopenRef::stderr),
+        "terminate" => ctx.new_rustfunc(PopenRef::terminate),
+        "kill" => ctx.new_rustfunc(PopenRef::kill),
+        "communicate" => ctx.new_rustfunc(PopenRef::communicate),
+        "pid" => ctx.new_property(PopenRef::pid),
     });
 
     let module = py_module!(vm, "subprocess", {
diff --git a/vm/src/stdlib/symtable.rs b/vm/src/stdlib/symtable.rs
index 692e1ce3b..b3ba19ffa 100644
--- a/vm/src/stdlib/symtable.rs
+++ b/vm/src/stdlib/symtable.rs
@@ -1,4 +1,3 @@
-use crate::eval::get_compile_mode;
 use crate::obj::objstr::PyStringRef;
 use crate::obj::objtype::PyClassRef;
 use crate::pyobject::{PyClassImpl, PyObjectRef, PyRef, PyResult, PyValue};
@@ -28,7 +27,10 @@ fn symtable_symtable(
     mode: PyStringRef,
     vm: &VirtualMachine,
 ) -> PyResult<PySymbolTableRef> {
-    let mode = get_compile_mode(vm, &mode.value)?;
+    let mode = mode
+        .as_str()
+        .parse::<compile::Mode>()
+        .map_err(|err| vm.new_value_error(err.to_string()))?;
     let symtable =
         source_to_symtable(&source.value, mode).map_err(|err| vm.new_syntax_error(&err))?;
 
@@ -39,7 +41,7 @@ fn symtable_symtable(
 fn source_to_symtable(
     source: &str,
     mode: compile::Mode,
-) -> Result<symboltable::SymbolScope, CompileError> {
+) -> Result<symboltable::SymbolTable, CompileError> {
     let symtable = match mode {
         compile::Mode::Exec | compile::Mode::Single => {
             let ast = parser::parse_program(source)?;
@@ -54,7 +56,7 @@ fn source_to_symtable(
     Ok(symtable)
 }
 
-fn to_py_symbol_table(name: String, symtable: symboltable::SymbolScope) -> PySymbolTable {
+fn to_py_symbol_table(name: String, symtable: symboltable::SymbolTable) -> PySymbolTable {
     PySymbolTable { name, symtable }
 }
 
@@ -64,7 +66,7 @@ type PySymbolRef = PyRef<PySymbol>;
 #[pyclass(name = "SymbolTable")]
 struct PySymbolTable {
     name: String,
-    symtable: symboltable::SymbolScope,
+    symtable: symboltable::SymbolTable,
 }
 
 impl fmt::Debug for PySymbolTable {
@@ -114,7 +116,7 @@ impl PySymbolTable {
     fn get_children(&self, vm: &VirtualMachine) -> PyResult {
         let children = self
             .symtable
-            .sub_scopes
+            .sub_tables
             .iter()
             .map(|s| {
                 to_py_symbol_table("bla".to_string(), s.clone())
@@ -152,12 +154,12 @@ impl PySymbol {
 
     #[pymethod(name = "is_global")]
     fn is_global(&self, vm: &VirtualMachine) -> PyResult {
-        Ok(vm.ctx.new_bool(self.symbol.is_global))
+        Ok(vm.ctx.new_bool(self.symbol.is_global()))
     }
 
     #[pymethod(name = "is_local")]
     fn is_local(&self, vm: &VirtualMachine) -> PyResult {
-        Ok(vm.ctx.new_bool(self.symbol.is_local))
+        Ok(vm.ctx.new_bool(self.symbol.is_local()))
     }
 
     #[pymethod(name = "is_referenced")]
diff --git a/vm/src/stdlib/thread.rs b/vm/src/stdlib/thread.rs
index 414e7d72e..225001c4d 100644
--- a/vm/src/stdlib/thread.rs
+++ b/vm/src/stdlib/thread.rs
@@ -37,7 +37,7 @@ fn get_ident(_vm: &VirtualMachine) -> u32 {
 
 fn allocate_lock(vm: &VirtualMachine) -> PyResult {
     let lock_class = vm.class("_thread", "RLock");
-    vm.invoke(lock_class.into_object(), vec![])
+    vm.invoke(&lock_class.into_object(), vec![])
 }
 
 pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
diff --git a/vm/src/stdlib/zlib.rs b/vm/src/stdlib/zlib.rs
new file mode 100644
index 000000000..9b731c6d2
--- /dev/null
+++ b/vm/src/stdlib/zlib.rs
@@ -0,0 +1,158 @@
+use crate::function::OptionalArg;
+use crate::obj::{objbytes::PyBytesRef, objint::PyIntRef};
+use crate::pyobject::{ItemProtocol, PyObjectRef, PyResult};
+use crate::types::create_type;
+use crate::vm::VirtualMachine;
+
+use adler32::RollingAdler32 as Adler32;
+use crc32fast::Hasher as Crc32;
+use flate2::{write::ZlibEncoder, Compression, Decompress, FlushDecompress, Status};
+use libz_sys as libz;
+use num_traits::cast::ToPrimitive;
+
+use std::io::Write;
+
+// copied from zlibmodule.c (commit 530f506ac91338)
+const MAX_WBITS: u8 = 15;
+const DEF_BUF_SIZE: usize = 16 * 1024;
+
+pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
+    let ctx = &vm.ctx;
+
+    let zlib_error = create_type(
+        "error",
+        &ctx.types.type_type,
+        &ctx.exceptions.exception_type,
+    );
+
+    py_module!(vm, "zlib", {
+        "crc32" => ctx.new_rustfunc(zlib_crc32),
+        "adler32" => ctx.new_rustfunc(zlib_adler32),
+        "compress" => ctx.new_rustfunc(zlib_compress),
+        "decompress" => ctx.new_rustfunc(zlib_decompress),
+        "error" => zlib_error,
+        "Z_DEFAULT_COMPRESSION" => ctx.new_int(libz::Z_DEFAULT_COMPRESSION),
+        "Z_NO_COMPRESSION" => ctx.new_int(libz::Z_NO_COMPRESSION),
+        "Z_BEST_SPEED" => ctx.new_int(libz::Z_BEST_SPEED),
+        "Z_BEST_COMPRESSION" => ctx.new_int(libz::Z_BEST_COMPRESSION),
+        "DEF_BUF_SIZE" => ctx.new_int(DEF_BUF_SIZE),
+        "MAX_WBITS" => ctx.new_int(MAX_WBITS),
+    })
+}
+
+/// Compute an Adler-32 checksum of data.
+fn zlib_adler32(
+    data: PyBytesRef,
+    begin_state: OptionalArg<PyIntRef>,
+    vm: &VirtualMachine,
+) -> PyResult<PyObjectRef> {
+    let data = data.get_value();
+
+    let begin_state = begin_state
+        .into_option()
+        .as_ref()
+        .map(|v| v.as_bigint().to_i32().unwrap())
+        .unwrap_or(1);
+
+    let mut hasher = Adler32::from_value(begin_state as u32);
+    hasher.update_buffer(data);
+
+    let checksum: u32 = hasher.hash();
+
+    Ok(vm.new_int(checksum))
+}
+
+/// Compute a CRC-32 checksum of data.
+fn zlib_crc32(
+    data: PyBytesRef,
+    begin_state: OptionalArg<PyIntRef>,
+    vm: &VirtualMachine,
+) -> PyResult<PyObjectRef> {
+    let data = data.get_value();
+
+    let begin_state = begin_state
+        .into_option()
+        .as_ref()
+        .map(|v| v.as_bigint().to_i32().unwrap())
+        .unwrap_or(0);
+
+    let mut hasher = Crc32::new_with_initial(begin_state as u32);
+    hasher.update(data);
+
+    let checksum: u32 = hasher.finalize();
+
+    Ok(vm.new_int(checksum))
+}
+
+/// Returns a bytes object containing compressed data.
+fn zlib_compress(
+    data: PyBytesRef,
+    level: OptionalArg<PyIntRef>,
+    vm: &VirtualMachine,
+) -> PyResult<PyObjectRef> {
+    let input_bytes = data.get_value();
+
+    let level = level
+        .into_option()
+        .as_ref()
+        .map(|v| v.as_bigint().to_i32().unwrap())
+        .unwrap_or(libz::Z_DEFAULT_COMPRESSION);
+
+    let compression = match level {
+        valid_level @ libz::Z_NO_COMPRESSION..=libz::Z_BEST_COMPRESSION => {
+            Compression::new(valid_level as u32)
+        }
+        libz::Z_DEFAULT_COMPRESSION => Compression::default(),
+        _ => return Err(zlib_error("Bad compression level", vm)),
+    };
+
+    let mut encoder = ZlibEncoder::new(Vec::new(), compression);
+    encoder.write_all(input_bytes).unwrap();
+    let encoded_bytes = encoder.finish().unwrap();
+
+    Ok(vm.ctx.new_bytes(encoded_bytes))
+}
+
+/// Returns a bytes object containing the uncompressed data.
+fn zlib_decompress(
+    data: PyBytesRef,
+    wbits: OptionalArg<PyIntRef>,
+    bufsize: OptionalArg<PyIntRef>,
+    vm: &VirtualMachine,
+) -> PyResult<PyObjectRef> {
+    let encoded_bytes = data.get_value();
+
+    let wbits = wbits
+        .into_option()
+        .as_ref()
+        .map(|wbits| wbits.as_bigint().to_u8().unwrap())
+        .unwrap_or(MAX_WBITS);
+
+    let bufsize = bufsize
+        .into_option()
+        .as_ref()
+        .map(|bufsize| bufsize.as_bigint().to_usize().unwrap())
+        .unwrap_or(DEF_BUF_SIZE);
+
+    let mut decompressor = Decompress::new_with_window_bits(true, wbits);
+    let mut decoded_bytes = Vec::with_capacity(bufsize);
+
+    match decompressor.decompress_vec(&encoded_bytes, &mut decoded_bytes, FlushDecompress::Finish) {
+        Ok(Status::BufError) => Err(zlib_error("inconsistent or truncated state", vm)),
+        Err(_) => Err(zlib_error("invalid input data", vm)),
+        _ => Ok(vm.ctx.new_bytes(decoded_bytes)),
+    }
+}
+
+fn zlib_error(message: &str, vm: &VirtualMachine) -> PyObjectRef {
+    let module = vm
+        .get_attribute(vm.sys_module.clone(), "modules")
+        .unwrap()
+        .get_item("zlib", vm)
+        .unwrap();
+
+    let zlib_error = vm.get_attribute(module, "error").unwrap();
+    let zlib_error = zlib_error.downcast().unwrap();
+
+    vm.new_exception(zlib_error, message.to_string())
+}
diff --git a/vm/src/sysmodule.rs b/vm/src/sysmodule.rs
index 66bcef0cc..2527e9d10 100644
--- a/vm/src/sysmodule.rs
+++ b/vm/src/sysmodule.rs
@@ -173,6 +173,16 @@ fn sys_exit(code: OptionalArg<i32>, _vm: &VirtualMachine) -> PyResult<()> {
     std::process::exit(code)
 }
 
+#[pystruct_sequence(name = "version_info")]
+#[derive(Default, Debug)]
+struct VersionInfo {
+    major: usize,
+    minor: usize,
+    micro: usize,
+    releaselevel: String,
+    serial: usize,
+}
+
 pub fn make_module(vm: &VirtualMachine, module: PyObjectRef, builtins: PyObjectRef) {
     let ctx = &vm.ctx;
 
@@ -181,6 +191,17 @@ pub fn make_module(vm: &VirtualMachine, module: PyObjectRef, builtins: PyObjectR
         .into_struct_sequence(vm, flags_type)
         .unwrap();
 
+    let version_info_type = VersionInfo::make_class(ctx);
+    let version_info = VersionInfo {
+        major: env!("CARGO_PKG_VERSION_MAJOR").parse().unwrap(),
+        minor: env!("CARGO_PKG_VERSION_MINOR").parse().unwrap(),
+        micro: env!("CARGO_PKG_VERSION_PATCH").parse().unwrap(),
+        releaselevel: "alpha".to_owned(),
+        serial: 0,
+    }
+    .into_struct_sequence(vm, version_info_type)
+    .unwrap();
+
     // TODO Add crate version to this namespace
     let implementation = py_namespace!(vm, {
         "name" => ctx.new_str("RustPython".to_string()),
@@ -302,6 +323,7 @@ settrace() -- set the global debug tracing function
 
     let prefix = option_env!("RUSTPYTHON_PREFIX").unwrap_or("/usr/local");
     let base_prefix = option_env!("RUSTPYTHON_BASEPREFIX").unwrap_or(prefix);
+    let exec_prefix = option_env!("RUSTPYTHON_EXECPREFIX").unwrap_or(prefix);
 
     extend_module!(vm, module, {
       "__name__" => ctx.new_str(String::from("sys")),
@@ -337,9 +359,11 @@ settrace() -- set the global debug tracing function
       "setprofile" => ctx.new_rustfunc(sys_setprofile),
       "settrace" => ctx.new_rustfunc(sys_settrace),
       "version" => vm.new_str(version::get_version()),
+      "version_info" => version_info,
       "exc_info" => ctx.new_rustfunc(sys_exc_info),
       "prefix" => ctx.new_str(prefix.to_string()),
       "base_prefix" => ctx.new_str(base_prefix.to_string()),
+      "exec_prefix" => ctx.new_str(exec_prefix.to_string()),
       "exit" => ctx.new_rustfunc(sys_exit),
     });
 
diff --git a/vm/src/types.rs b/vm/src/types.rs
new file mode 100644
index 000000000..048b3d8ad
--- /dev/null
+++ b/vm/src/types.rs
@@ -0,0 +1,313 @@
+use crate::obj::objbool;
+use crate::obj::objbytearray;
+use crate::obj::objbytes;
+use crate::obj::objclassmethod;
+use crate::obj::objcode;
+use crate::obj::objcomplex;
+use crate::obj::objdict;
+use crate::obj::objellipsis;
+use crate::obj::objenumerate;
+use crate::obj::objfilter;
+use crate::obj::objfloat;
+use crate::obj::objframe;
+use crate::obj::objfunction;
+use crate::obj::objgenerator;
+use crate::obj::objint;
+use crate::obj::objiter;
+use crate::obj::objlist;
+use crate::obj::objmap;
+use crate::obj::objmappingproxy;
+use crate::obj::objmemory;
+use crate::obj::objmodule;
+use crate::obj::objnamespace;
+use crate::obj::objnone;
+use crate::obj::objobject;
+use crate::obj::objproperty;
+use crate::obj::objrange;
+use crate::obj::objset;
+use crate::obj::objslice;
+use crate::obj::objstaticmethod;
+use crate::obj::objstr;
+use crate::obj::objsuper;
+use crate::obj::objtuple;
+use crate::obj::objtype::{self, PyClass, PyClassRef};
+use crate::obj::objweakproxy;
+use crate::obj::objweakref;
+use crate::obj::objzip;
+use crate::pyobject::{PyAttributes, PyContext, PyObject, PyObjectRef};
+use std::cell::RefCell;
+use std::mem;
+use std::ptr;
+
+/// Holder of references to builtin types.
+#[derive(Debug)]
+pub struct TypeZoo {
+    pub bytes_type: PyClassRef,
+    pub bytesiterator_type: PyClassRef,
+    pub bytearray_type: PyClassRef,
+    pub bytearrayiterator_type: PyClassRef,
+    pub bool_type: PyClassRef,
+    pub classmethod_type: PyClassRef,
+    pub code_type: PyClassRef,
+    pub dict_type: PyClassRef,
+    pub enumerate_type: PyClassRef,
+    pub filter_type: PyClassRef,
+    pub float_type: PyClassRef,
+    pub frame_type: PyClassRef,
+    pub frozenset_type: PyClassRef,
+    pub generator_type: PyClassRef,
+    pub int_type: PyClassRef,
+    pub iter_type: PyClassRef,
+    pub complex_type: PyClassRef,
+    pub list_type: PyClassRef,
+    pub listiterator_type: PyClassRef,
+    pub listreverseiterator_type: PyClassRef,
+    pub striterator_type: PyClassRef,
+    pub strreverseiterator_type: PyClassRef,
+    pub dictkeyiterator_type: PyClassRef,
+    pub dictvalueiterator_type: PyClassRef,
+    pub dictitemiterator_type: PyClassRef,
+    pub dictkeys_type: PyClassRef,
+    pub dictvalues_type: PyClassRef,
+    pub dictitems_type: PyClassRef,
+    pub map_type: PyClassRef,
+    pub memoryview_type: PyClassRef,
+    pub tuple_type: PyClassRef,
+    pub tupleiterator_type: PyClassRef,
+    pub set_type: PyClassRef,
+    pub staticmethod_type: PyClassRef,
+    pub super_type: PyClassRef,
+    pub str_type: PyClassRef,
+    pub range_type: PyClassRef,
+    pub rangeiterator_type: PyClassRef,
+    pub slice_type: PyClassRef,
+    pub type_type: PyClassRef,
+    pub zip_type: PyClassRef,
+    pub function_type: PyClassRef,
+    pub builtin_function_or_method_type: PyClassRef,
+    pub property_type: PyClassRef,
+    pub readonly_property_type: PyClassRef,
+    pub module_type: PyClassRef,
+    pub namespace_type: PyClassRef,
+    pub bound_method_type: PyClassRef,
+    pub weakref_type: PyClassRef,
+    pub weakproxy_type: PyClassRef,
+    pub mappingproxy_type: PyClassRef,
+    pub object_type: PyClassRef,
+}
+
+impl Default for TypeZoo {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl TypeZoo {
+    pub fn new() -> Self {
+        let (type_type, object_type) = init_type_hierarchy();
+
+        let dict_type = create_type("dict", &type_type, &object_type);
+        let module_type = create_type("module", &type_type, &object_type);
+        let namespace_type = create_type("SimpleNamespace", &type_type, &object_type);
+        let classmethod_type = create_type("classmethod", &type_type, &object_type);
+        let staticmethod_type = create_type("staticmethod", &type_type, &object_type);
+        let function_type = create_type("function", &type_type, &object_type);
+        let builtin_function_or_method_type =
+            create_type("builtin_function_or_method", &type_type, &object_type);
+        let property_type = create_type("property", &type_type, &object_type);
+        let readonly_property_type = create_type("readonly_property", &type_type, &object_type);
+        let super_type = create_type("super", &type_type, &object_type);
+        let weakref_type = create_type("ref", &type_type, &object_type);
+        let weakproxy_type = create_type("weakproxy", &type_type, &object_type);
+        let generator_type = create_type("generator", &type_type, &object_type);
+        let bound_method_type = create_type("method", &type_type, &object_type);
+        let str_type = create_type("str", &type_type, &object_type);
+        let list_type = create_type("list", &type_type, &object_type);
+        let listiterator_type = create_type("list_iterator", &type_type, &object_type);
+        let listreverseiterator_type =
+            create_type("list_reverseiterator", &type_type, &object_type);
+        let striterator_type = create_type("str_iterator", &type_type, &object_type);
+        let strreverseiterator_type = create_type("str_reverseiterator", &type_type, &object_type);
+        let dictkeys_type = create_type("dict_keys", &type_type, &object_type);
+        let dictvalues_type = create_type("dict_values", &type_type, &object_type);
+        let dictitems_type = create_type("dict_items", &type_type, &object_type);
+        let dictkeyiterator_type = create_type("dict_keyiterator", &type_type, &object_type);
+        let dictvalueiterator_type = create_type("dict_valueiterator", &type_type, &object_type);
+        let dictitemiterator_type = create_type("dict_itemiterator", &type_type, &object_type);
+        let set_type = create_type("set", &type_type, &object_type);
+        let frozenset_type = create_type("frozenset", &type_type, &object_type);
+        let int_type = create_type("int", &type_type, &object_type);
+        let float_type = create_type("float", &type_type, &object_type);
+        let frame_type = create_type("frame", &type_type, &object_type);
+        let complex_type = create_type("complex", &type_type, &object_type);
+        let bytes_type = create_type("bytes", &type_type, &object_type);
+        let bytesiterator_type = create_type("bytes_iterator", &type_type, &object_type);
+        let bytearray_type = create_type("bytearray", &type_type, &object_type);
+        let bytearrayiterator_type = create_type("bytearray_iterator", &type_type, &object_type);
+        let tuple_type = create_type("tuple", &type_type, &object_type);
+        let tupleiterator_type = create_type("tuple_iterator", &type_type, &object_type);
+        let iter_type = create_type("iter", &type_type, &object_type);
+        let enumerate_type = create_type("enumerate", &type_type, &object_type);
+        let filter_type = create_type("filter", &type_type, &object_type);
+        let map_type = create_type("map", &type_type, &object_type);
+        let zip_type = create_type("zip", &type_type, &object_type);
+        let bool_type = create_type("bool", &type_type, &int_type);
+        let memoryview_type = create_type("memoryview", &type_type, &object_type);
+        let code_type = create_type("code", &type_type, &object_type);
+        let range_type = create_type("range", &type_type, &object_type);
+        let rangeiterator_type = create_type("range_iterator", &type_type, &object_type);
+        let slice_type = create_type("slice", &type_type, &object_type);
+        let mappingproxy_type = create_type("mappingproxy", &type_type, &object_type);
+
+        Self {
+            bool_type,
+            memoryview_type,
+            bytearray_type,
+            bytearrayiterator_type,
+            bytes_type,
+            bytesiterator_type,
+            code_type,
+            complex_type,
+            classmethod_type,
+            int_type,
+            float_type,
+            frame_type,
+            staticmethod_type,
+            list_type,
+            listiterator_type,
+            listreverseiterator_type,
+            striterator_type,
+            strreverseiterator_type,
+            dictkeys_type,
+            dictvalues_type,
+            dictitems_type,
+            dictkeyiterator_type,
+            dictvalueiterator_type,
+            dictitemiterator_type,
+            set_type,
+            frozenset_type,
+            tuple_type,
+            tupleiterator_type,
+            iter_type,
+            enumerate_type,
+            filter_type,
+            map_type,
+            zip_type,
+            dict_type,
+            str_type,
+            range_type,
+            rangeiterator_type,
+            slice_type,
+            object_type,
+            function_type,
+            builtin_function_or_method_type,
+            super_type,
+            mappingproxy_type,
+            property_type,
+            readonly_property_type,
+            generator_type,
+            module_type,
+            namespace_type,
+            bound_method_type,
+            weakref_type,
+            weakproxy_type,
+            type_type,
+        }
+    }
+}
+
+pub fn create_type(name: &str, type_type: &PyClassRef, base: &PyClassRef) -> PyClassRef {
+    let dict = PyAttributes::new();
+    objtype::new(type_type.clone(), name, vec![base.clone()], dict).unwrap()
+}
+
+fn init_type_hierarchy() -> (PyClassRef, PyClassRef) {
+    // `type` inherits from `object`
+    // and both `type` and `object are instances of `type`.
+    // to produce this circular dependency, we need an unsafe block.
+    // (and yes, this will never get dropped. TODO?)
+    let (type_type, object_type) = unsafe {
+        let object_type = PyObject {
+            typ: mem::uninitialized(), // !
+            dict: None,
+            payload: PyClass {
+                name: String::from("object"),
+                mro: vec![],
+                subclasses: RefCell::new(vec![]),
+                attributes: RefCell::new(PyAttributes::new()),
+            },
+        }
+        .into_ref();
+
+        let type_type = PyObject {
+            typ: mem::uninitialized(), // !
+            dict: None,
+            payload: PyClass {
+                name: String::from("type"),
+                mro: vec![object_type.clone().downcast().unwrap()],
+                subclasses: RefCell::new(vec![]),
+                attributes: RefCell::new(PyAttributes::new()),
+            },
+        }
+        .into_ref();
+
+        let object_type_ptr = PyObjectRef::into_raw(object_type.clone()) as *mut PyObject<PyClass>;
+        let type_type_ptr = PyObjectRef::into_raw(type_type.clone()) as *mut PyObject<PyClass>;
+
+        let type_type: PyClassRef = type_type.downcast().unwrap();
+        let object_type: PyClassRef = object_type.downcast().unwrap();
+
+        ptr::write(&mut (*object_type_ptr).typ, type_type.clone());
+        ptr::write(&mut (*type_type_ptr).typ, type_type.clone());
+
+        (type_type, object_type)
+    };
+
+    object_type
+        .subclasses
+        .borrow_mut()
+        .push(objweakref::PyWeak::downgrade(&type_type.as_object()));
+
+    (type_type, object_type)
+}
+
+/// Fill attributes of builtin types.
+pub fn initialize_types(context: &PyContext) {
+    objtype::init(&context);
+    objlist::init(&context);
+    objset::init(&context);
+    objtuple::init(&context);
+    objobject::init(&context);
+    objdict::init(&context);
+    objfunction::init(&context);
+    objstaticmethod::init(&context);
+    objclassmethod::init(&context);
+    objgenerator::init(&context);
+    objint::init(&context);
+    objfloat::init(&context);
+    objcomplex::init(&context);
+    objbytes::init(&context);
+    objbytearray::init(&context);
+    objproperty::init(&context);
+    objmemory::init(&context);
+    objstr::init(&context);
+    objrange::init(&context);
+    objslice::init(&context);
+    objsuper::init(&context);
+    objtuple::init(&context);
+    objiter::init(&context);
+    objellipsis::init(&context);
+    objenumerate::init(&context);
+    objfilter::init(&context);
+    objmap::init(&context);
+    objzip::init(&context);
+    objbool::init(&context);
+    objcode::init(&context);
+    objframe::init(&context);
+    objweakref::init(&context);
+    objweakproxy::init(&context);
+    objnone::init(&context);
+    objmodule::init(&context);
+    objnamespace::init(&context);
+    objmappingproxy::init(&context);
+}
diff --git a/vm/src/vm.rs b/vm/src/vm.rs
index fdeff8e12..ce9382eaf 100644
--- a/vm/src/vm.rs
+++ b/vm/src/vm.rs
@@ -25,6 +25,7 @@ use crate::obj::objfunction::{PyFunction, PyMethod};
 use crate::obj::objgenerator::PyGenerator;
 use crate::obj::objint::PyInt;
 use crate::obj::objiter;
+use crate::obj::objmodule::{self, PyModule};
 use crate::obj::objsequence;
 use crate::obj::objstr::{PyString, PyStringRef};
 use crate::obj::objtuple::PyTupleRef;
@@ -32,8 +33,8 @@ use crate::obj::objtype;
 use crate::obj::objtype::PyClassRef;
 use crate::pyhash;
 use crate::pyobject::{
-    IdProtocol, ItemProtocol, PyContext, PyObjectRef, PyResult, PyValue, TryFromObject, TryIntoRef,
-    TypeProtocol,
+    IdProtocol, ItemProtocol, PyContext, PyObject, PyObjectRef, PyResult, PyValue, TryFromObject,
+    TryIntoRef, TypeProtocol,
 };
 use crate::scope::Scope;
 use crate::stdlib;
@@ -142,9 +143,23 @@ impl VirtualMachine {
         flame_guard!("init VirtualMachine");
         let ctx = PyContext::new();
 
+        // make a new module without access to the vm; doesn't
+        // set __spec__, __loader__, etc. attributes
+        let new_module = |name: &str, dict| {
+            PyObject::new(
+                PyModule {
+                    name: name.to_owned(),
+                },
+                ctx.types.module_type.clone(),
+                Some(dict),
+            )
+        };
+
         // Hard-core modules:
-        let builtins = ctx.new_module("builtins", ctx.new_dict());
-        let sysmod = ctx.new_module("sys", ctx.new_dict());
+        let builtins_dict = ctx.new_dict();
+        let builtins = new_module("builtins", builtins_dict.clone());
+        let sysmod_dict = ctx.new_dict();
+        let sysmod = new_module("sys", sysmod_dict.clone());
 
         let stdlib_inits = RefCell::new(stdlib::get_module_inits());
         let frozen = RefCell::new(frozen::get_module_inits());
@@ -168,6 +183,19 @@ impl VirtualMachine {
             signal_handlers: Default::default(),
         };
 
+        objmodule::init_module_dict(
+            &vm,
+            &builtins_dict,
+            vm.new_str("builtins".to_owned()),
+            vm.get_none(),
+        );
+        objmodule::init_module_dict(
+            &vm,
+            &sysmod_dict,
+            vm.new_str("sys".to_owned()),
+            vm.get_none(),
+        );
+
         builtins::make_module(&vm, builtins.clone());
         sysmodule::make_module(&vm, sysmod, builtins);
         vm
@@ -254,11 +282,22 @@ impl VirtualMachine {
         self.ctx.new_bool(b)
     }
 
+    pub fn new_module(&self, name: &str, dict: PyDictRef) -> PyObjectRef {
+        objmodule::init_module_dict(self, &dict, self.new_str(name.to_owned()), self.get_none());
+        PyObject::new(
+            PyModule {
+                name: name.to_owned(),
+            },
+            self.ctx.types.module_type.clone(),
+            Some(dict),
+        )
+    }
+
     #[cfg_attr(feature = "flame-it", flame("VirtualMachine"))]
     fn new_exception_obj(&self, exc_type: PyClassRef, args: Vec<PyObjectRef>) -> PyResult {
         // TODO: add repr of args into logging?
         vm_trace!("New exception created: {}", exc_type.name);
-        self.invoke(exc_type.into_object(), args)
+        self.invoke(&exc_type.into_object(), args)
     }
 
     pub fn new_empty_exception(&self, exc_type: PyClassRef) -> PyResult {
@@ -407,10 +446,23 @@ impl VirtualMachine {
     }
 
     pub fn import(&self, module: &str, from_list: &PyObjectRef, level: usize) -> PyResult {
-        let sys_modules = self.get_attribute(self.sys_module.clone(), "modules")?;
-        sys_modules
-            .get_item(module.to_string(), self)
-            .or_else(|_| {
+        // if the import inputs seem weird, e.g a package import or something, rather than just
+        // a straight `import ident`
+        let weird = module.contains('.')
+            || level != 0
+            || objbool::boolval(self, from_list.clone()).unwrap_or(true);
+
+        let module = self.new_str(module.to_owned());
+
+        let cached_module = if weird {
+            None
+        } else {
+            let sys_modules = self.get_attribute(self.sys_module.clone(), "modules")?;
+            sys_modules.get_item(module.clone(), self).ok()
+        };
+        match cached_module {
+            Some(module) => Ok(module),
+            None => {
                 let import_func = self
                     .get_attribute(self.builtins.clone(), "__import__")
                     .map_err(|_| self.new_import_error("__import__ not found".to_string()))?;
@@ -424,17 +476,18 @@ impl VirtualMachine {
                     (self.get_none(), self.get_none())
                 };
                 self.invoke(
-                    import_func,
+                    &import_func,
                     vec![
-                        self.ctx.new_str(module.to_string()),
+                        module,
                         globals,
                         locals,
                         from_list.clone(),
                         self.ctx.new_int(level),
                     ],
                 )
-            })
-            .map_err(|exc| import::remove_importlib_frames(self, &exc))
+                .map_err(|exc| import::remove_importlib_frames(self, &exc))
+            }
+        }
     }
 
     /// Determines if `obj` is an instance of `cls`, either directly, indirectly or virtually via
@@ -463,7 +516,7 @@ impl VirtualMachine {
 
     pub fn call_get_descriptor(&self, attr: PyObjectRef, obj: PyObjectRef) -> PyResult {
         let attr_class = attr.class();
-        if let Some(descriptor) = objtype::class_get_attr(&attr_class, "__get__") {
+        if let Some(ref descriptor) = objtype::class_get_attr(&attr_class, "__get__") {
             let cls = obj.class();
             self.invoke(descriptor, vec![attr, obj.clone(), cls.into_object()])
         } else {
@@ -487,14 +540,14 @@ impl VirtualMachine {
                     func
                 );
                 let wrapped = self.call_get_descriptor(func, obj.clone())?;
-                self.invoke(wrapped, args)
+                self.invoke(&wrapped, args)
             }
             None => Err(self.new_type_error(format!("Unsupported method: {}", method_name))),
         }
     }
 
     #[cfg_attr(feature = "flame-it", flame("VirtualMachine"))]
-    fn _invoke(&self, func_ref: PyObjectRef, args: PyFuncArgs) -> PyResult {
+    fn _invoke(&self, func_ref: &PyObjectRef, args: PyFuncArgs) -> PyResult {
         vm_trace!("Invoke: {:?} {:?}", func_ref, args);
 
         if let Some(PyFunction {
@@ -513,7 +566,7 @@ impl VirtualMachine {
             ref object,
         }) = func_ref.payload()
         {
-            self.invoke(function.clone(), args.insert(object.clone()))
+            self.invoke(&function, args.insert(object.clone()))
         } else if let Some(PyBuiltinFunction { ref value }) = func_ref.payload() {
             value(self, args)
         } else {
@@ -523,9 +576,8 @@ impl VirtualMachine {
         }
     }
 
-    // TODO: make func_ref an &PyObjectRef
     #[inline]
-    pub fn invoke<T>(&self, func_ref: PyObjectRef, args: T) -> PyResult
+    pub fn invoke<T>(&self, func_ref: &PyObjectRef, args: T) -> PyResult
     where
         T: Into<PyFuncArgs>,
     {
@@ -546,7 +598,7 @@ impl VirtualMachine {
             let trace_func = self.trace_func.borrow().clone();
             if !self.is_none(&trace_func) {
                 self.use_tracing.replace(false);
-                let res = self.invoke(trace_func, args.clone());
+                let res = self.invoke(&trace_func, args.clone());
                 self.use_tracing.replace(true);
                 res?;
             }
@@ -554,7 +606,7 @@ impl VirtualMachine {
             let profile_func = self.profile_func.borrow().clone();
             if !self.is_none(&profile_func) {
                 self.use_tracing.replace(false);
-                let res = self.invoke(profile_func, args);
+                let res = self.invoke(&profile_func, args);
                 self.use_tracing.replace(true);
                 res?;
             }
@@ -592,7 +644,7 @@ impl VirtualMachine {
 
     pub fn invoke_with_locals(
         &self,
-        function: PyObjectRef,
+        function: &PyObjectRef,
         cells: PyDictRef,
         locals: PyDictRef,
     ) -> PyResult {
@@ -605,7 +657,7 @@ impl VirtualMachine {
         }
         panic!(
             "invoke_with_locals: expected python function, got: {:?}",
-            function
+            *function
         );
     }
 
@@ -831,7 +883,7 @@ impl VirtualMachine {
     {
         if let Some(method_or_err) = self.get_method(obj.clone(), method) {
             let method = method_or_err?;
-            let result = self.invoke(method, vec![arg.clone()])?;
+            let result = self.invoke(&method, vec![arg.clone()])?;
             if !result.is(&self.ctx.not_implemented()) {
                 return Ok(result);
             }
@@ -864,6 +916,43 @@ impl VirtualMachine {
         })
     }
 
+    pub fn generic_getattribute(
+        &self,
+        obj: PyObjectRef,
+        name_str: PyStringRef,
+    ) -> PyResult<Option<PyObjectRef>> {
+        let name = name_str.as_str();
+        let cls = obj.class();
+
+        if let Some(attr) = objtype::class_get_attr(&cls, &name) {
+            let attr_class = attr.class();
+            if objtype::class_has_attr(&attr_class, "__set__") {
+                if let Some(descriptor) = objtype::class_get_attr(&attr_class, "__get__") {
+                    return self
+                        .invoke(&descriptor, vec![attr, obj, cls.into_object()])
+                        .map(Some);
+                }
+            }
+        }
+
+        let attr = if let Some(ref dict) = obj.dict {
+            dict.get_item_option(name_str.clone(), self)?
+        } else {
+            None
+        };
+
+        if let Some(obj_attr) = attr {
+            Ok(Some(obj_attr))
+        } else if let Some(attr) = objtype::class_get_attr(&cls, &name) {
+            self.call_get_descriptor(attr, obj).map(Some)
+        } else if let Some(getter) = objtype::class_get_attr(&cls, "__getattr__") {
+            self.invoke(&getter, vec![obj, name_str.into_object()])
+                .map(Some)
+        } else {
+            Ok(None)
+        }
+    }
+
     pub fn is_callable(&self, obj: &PyObjectRef) -> bool {
         match_class!(obj,
             PyFunction => true,
@@ -877,7 +966,7 @@ impl VirtualMachine {
     pub fn compile(
         &self,
         source: &str,
-        mode: &compile::Mode,
+        mode: compile::Mode,
         source_path: String,
     ) -> Result<PyCodeRef, CompileError> {
         compile::compile(source, mode, source_path, self.settings.optimize)
@@ -1132,7 +1221,7 @@ impl VirtualMachine {
     pub fn _membership(&self, haystack: PyObjectRef, needle: PyObjectRef) -> PyResult {
         if let Some(method_or_err) = self.get_method(haystack.clone(), "__contains__") {
             let method = method_or_err?;
-            self.invoke(method, vec![needle])
+            self.invoke(&method, vec![needle])
         } else {
             self._membership_iter_search(haystack, needle)
         }
diff --git a/wasm/lib/src/browser_module.rs b/wasm/lib/src/browser_module.rs
index fed4fcbdc..abfdc2b53 100644
--- a/wasm/lib/src/browser_module.rs
+++ b/wasm/lib/src/browser_module.rs
@@ -133,7 +133,7 @@ fn browser_request_animation_frame(func: PyCallable, vm: &VirtualMachine) -> PyR
         let vm = &stored_vm.vm;
         let func = func.clone();
         let args = vec![vm.ctx.new_float(time)];
-        let _ = vm.invoke(func.into_object(), args);
+        let _ = vm.invoke(&func.into_object(), args);
 
         let closure = f.borrow_mut().take();
         drop(closure);
@@ -212,12 +212,12 @@ impl PyPromise {
                     } else {
                         vec![convert::js_to_py(vm, val)]
                     };
-                    vm.invoke(on_fulfill.into_object(), PyFuncArgs::new(args, vec![]))
+                    vm.invoke(&on_fulfill.into_object(), PyFuncArgs::new(args, vec![]))
                 }
                 Err(err) => {
                     if let OptionalArg::Present(on_reject) = on_reject {
                         let err = convert::js_to_py(vm, err);
-                        vm.invoke(on_reject.into_object(), PyFuncArgs::new(vec![err], vec![]))
+                        vm.invoke(&on_reject.into_object(), PyFuncArgs::new(vec![err], vec![]))
                     } else {
                         return Err(err);
                     }
@@ -240,7 +240,7 @@ impl PyPromise {
                     .expect("that the vm is valid when the promise resolves");
                 let vm = &stored_vm.vm;
                 let err = convert::js_to_py(vm, err);
-                let res = vm.invoke(on_reject.into_object(), PyFuncArgs::new(vec![err], vec![]));
+                let res = vm.invoke(&on_reject.into_object(), PyFuncArgs::new(vec![err], vec![]));
                 convert::pyresult_to_jsresult(vm, res)
             })
         });
diff --git a/wasm/lib/src/convert.rs b/wasm/lib/src/convert.rs
index f4c71e60d..16b7fe3f7 100644
--- a/wasm/lib/src/convert.rs
+++ b/wasm/lib/src/convert.rs
@@ -94,7 +94,7 @@ pub fn py_to_js(vm: &VirtualMachine, py_obj: PyObjectRef) -> JsValue {
                                 .insert(js_sys::JsString::from(key).into(), js_to_py(vm, val));
                         }
                     }
-                    let result = vm.invoke(py_obj.clone(), py_func_args);
+                    let result = vm.invoke(&py_obj, py_func_args);
                     pyresult_to_jsresult(vm, result)
                 };
             let closure = Closure::wrap(Box::new(closure)
diff --git a/wasm/lib/src/js_module.rs b/wasm/lib/src/js_module.rs
index 9468aa416..9622613f7 100644
--- a/wasm/lib/src/js_module.rs
+++ b/wasm/lib/src/js_module.rs
@@ -1,9 +1,8 @@
 use js_sys::{Array, Object, Reflect};
 use rustpython_vm::function::Args;
 use rustpython_vm::obj::{objfloat::PyFloatRef, objstr::PyStringRef, objtype::PyClassRef};
-use rustpython_vm::pyobject::{
-    create_type, PyClassImpl, PyObjectRef, PyRef, PyResult, PyValue, TryFromObject,
-};
+use rustpython_vm::pyobject::{PyClassImpl, PyObjectRef, PyRef, PyResult, PyValue, TryFromObject};
+use rustpython_vm::types::create_type;
 use rustpython_vm::VirtualMachine;
 use wasm_bindgen::{prelude::*, JsCast};
 
@@ -244,7 +243,7 @@ fn new_js_error(vm: &VirtualMachine, err: JsValue) -> PyObjectRef {
 pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
     let ctx = &vm.ctx;
     py_module!(vm, "_js", {
-        "JsError" => create_type("JsError", &ctx.type_type, &ctx.exceptions.exception_type),
+        "JsError" => create_type("JsError", &ctx.type_type(), &ctx.exceptions.exception_type),
         "JsValue" => PyJsValue::make_class(ctx),
     })
 }
diff --git a/wasm/lib/src/lib.rs b/wasm/lib/src/lib.rs
index 52049ee07..e750ef977 100644
--- a/wasm/lib/src/lib.rs
+++ b/wasm/lib/src/lib.rs
@@ -63,7 +63,7 @@ const TS_CMT_START: &'static str = "/*";
 ///     receive the Python kwargs as the `this` argument.
 /// -   `stdout?`: `(out: string) => void`: A function to replace the native print
 ///     function, by default `console.log`.
-pub fn eval_py(source: String, options: Option<Object>) -> Result<JsValue, JsValue> {
+pub fn eval_py(source: &str, options: Option<Object>) -> Result<JsValue, JsValue> {
     let options = options.unwrap_or_else(Object::new);
     let js_vars = {
         let prop = Reflect::get(&options, &"vars".into())?;
diff --git a/wasm/lib/src/vm_class.rs b/wasm/lib/src/vm_class.rs
index c75b68d6e..1f2584f0a 100644
--- a/wasm/lib/src/vm_class.rs
+++ b/wasm/lib/src/vm_class.rs
@@ -256,7 +256,7 @@ impl WASMVirtualMachine {
             let mod_name = name.clone();
 
             let stdlib_init_fn = move |vm: &VirtualMachine| {
-                let module = vm.ctx.new_module(&name, vm.ctx.new_dict());
+                let module = vm.new_module(&name, vm.ctx.new_dict());
                 for (key, value) in module_items.clone() {
                     vm.set_attr(&module, key, value).unwrap();
                 }
@@ -271,13 +271,13 @@ impl WASMVirtualMachine {
         })?
     }
 
-    fn run(&self, source: String, mode: compile::Mode) -> Result<JsValue, JsValue> {
+    fn run(&self, source: &str, mode: compile::Mode) -> Result<JsValue, JsValue> {
         self.assert_valid()?;
         self.with_unchecked(
             |StoredVirtualMachine {
                  ref vm, ref scope, ..
              }| {
-                let code = vm.compile(&source, &mode, "<wasm>".to_string());
+                let code = vm.compile(source, mode, "<wasm>".to_string());
                 let code = code.map_err(|err| {
                     let js_err = SyntaxError::new(&format!("Error parsing Python code: {}", err));
                     let _ =
@@ -295,16 +295,16 @@ impl WASMVirtualMachine {
         )
     }
 
-    pub fn exec(&self, source: String) -> Result<JsValue, JsValue> {
+    pub fn exec(&self, source: &str) -> Result<JsValue, JsValue> {
         self.run(source, compile::Mode::Exec)
     }
 
-    pub fn eval(&self, source: String) -> Result<JsValue, JsValue> {
+    pub fn eval(&self, source: &str) -> Result<JsValue, JsValue> {
         self.run(source, compile::Mode::Eval)
     }
 
     #[wasm_bindgen(js_name = execSingle)]
-    pub fn exec_single(&self, source: String) -> Result<JsValue, JsValue> {
+    pub fn exec_single(&self, source: &str) -> Result<JsValue, JsValue> {
         self.run(source, compile::Mode::Single)
     }
 }