diff --git a/Cargo.lock b/Cargo.lock
index c9c78ffe6..881852168 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1640,6 +1640,7 @@ dependencies = [
  "socket2",
  "statrs",
  "thread_local",
+ "timsort",
  "uname",
  "unic-char-property",
  "unic-normal",
@@ -1984,6 +1985,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "timsort"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9a035368bf2997adda2f78c1e2683e2b8e8f584e349e8cb7f8adf294b0a4ad70"
+
 [[package]]
 name = "tinyvec"
 version = "0.3.4"
diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index 6049b1f80..59b5c7227 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -873,7 +873,6 @@ class BuiltinTest(unittest.TestCase):
             m2 = map(map_char, "Is this the real life?")
             self.check_iter_pickle(m1, list(m2), proto)
 
-    @unittest.skip("TODO: RUSTPYTHON")
     def test_max(self):
         self.assertEqual(max('123123'), '3')
         self.assertEqual(max(1, 2, 3), 3)
diff --git a/Lib/test/test_sort.py b/Lib/test/test_sort.py
new file mode 100644
index 000000000..312d8a635
--- /dev/null
+++ b/Lib/test/test_sort.py
@@ -0,0 +1,390 @@
+from test import support
+import random
+import unittest
+from functools import cmp_to_key
+
+verbose = support.verbose
+nerrors = 0
+
+
+def check(tag, expected, raw, compare=None):
+    global nerrors
+
+    if verbose:
+        print("    checking", tag)
+
+    orig = raw[:]   # save input in case of error
+    if compare:
+        raw.sort(key=cmp_to_key(compare))
+    else:
+        raw.sort()
+
+    if len(expected) != len(raw):
+        print("error in", tag)
+        print("length mismatch;", len(expected), len(raw))
+        print(expected)
+        print(orig)
+        print(raw)
+        nerrors += 1
+        return
+
+    for i, good in enumerate(expected):
+        maybe = raw[i]
+        if good is not maybe:
+            print("error in", tag)
+            print("out of order at index", i, good, maybe)
+            print(expected)
+            print(orig)
+            print(raw)
+            nerrors += 1
+            return
+
+class TestBase(unittest.TestCase):
+    def testStressfully(self):
+        # Try a variety of sizes at and around powers of 2, and at powers of 10.
+        sizes = [0]
+        for power in range(1, 10):
+            n = 2 ** power
+            sizes.extend(range(n-1, n+2))
+        sizes.extend([10, 100, 1000])
+
+        class Complains(object):
+            maybe_complain = True
+
+            def __init__(self, i):
+                self.i = i
+
+            def __lt__(self, other):
+                if Complains.maybe_complain and random.random() < 0.001:
+                    if verbose:
+                        print("        complaining at", self, other)
+                    raise RuntimeError
+                return self.i < other.i
+
+            def __repr__(self):
+                return "Complains(%d)" % self.i
+
+        class Stable(object):
+            def __init__(self, key, i):
+                self.key = key
+                self.index = i
+
+            def __lt__(self, other):
+                return self.key < other.key
+
+            def __repr__(self):
+                return "Stable(%d, %d)" % (self.key, self.index)
+
+        for n in sizes:
+            x = list(range(n))
+            if verbose:
+                print("Testing size", n)
+
+            s = x[:]
+            check("identity", x, s)
+
+            s = x[:]
+            s.reverse()
+            check("reversed", x, s)
+
+            s = x[:]
+            random.shuffle(s)
+            check("random permutation", x, s)
+
+            y = x[:]
+            y.reverse()
+            s = x[:]
+            check("reversed via function", y, s, lambda a, b: (b>a)-(b<a))
+
+            if verbose:
+                print("    Checking against an insane comparison function.")
+                print("        If the implementation isn't careful, this may segfault.")
+            s = x[:]
+            s.sort(key=cmp_to_key(lambda a, b:  int(random.random() * 3) - 1))
+            check("an insane function left some permutation", x, s)
+
+            if len(x) >= 2:
+                def bad_key(x):
+                    raise RuntimeError
+                s = x[:]
+                self.assertRaises(RuntimeError, s.sort, key=bad_key)
+
+            x = [Complains(i) for i in x]
+            s = x[:]
+            random.shuffle(s)
+            Complains.maybe_complain = True
+            it_complained = False
+            try:
+                s.sort()
+            except RuntimeError:
+                it_complained = True
+            if it_complained:
+                Complains.maybe_complain = False
+                check("exception during sort left some permutation", x, s)
+
+            s = [Stable(random.randrange(10), i) for i in range(n)]
+            augmented = [(e, e.index) for e in s]
+            augmented.sort()    # forced stable because ties broken by index
+            x = [e for e, i in augmented] # a stable sort of s
+            check("stability", x, s)
+
+#==============================================================================
+
+class TestBugs(unittest.TestCase):
+
+    @unittest.skip("TODO: RUSTPYTHON; figure out how to detect sort mutation that doesn't change list length")
+    def test_bug453523(self):
+        # bug 453523 -- list.sort() crasher.
+        # If this fails, the most likely outcome is a core dump.
+        # Mutations during a list sort should raise a ValueError.
+
+        class C:
+            def __lt__(self, other):
+                if L and random.random() < 0.75:
+                    L.pop()
+                else:
+                    L.append(3)
+                return random.random() < 0.5
+
+        L = [C() for i in range(50)]
+        self.assertRaises(ValueError, L.sort)
+
+    @unittest.skip("TODO: RUSTPYTHON; figure out how to detect sort mutation that doesn't change list length")
+    def test_undetected_mutation(self):
+        # Python 2.4a1 did not always detect mutation
+        memorywaster = []
+        for i in range(20):
+            def mutating_cmp(x, y):
+                L.append(3)
+                L.pop()
+                return (x > y) - (x < y)
+            L = [1,2]
+            self.assertRaises(ValueError, L.sort, key=cmp_to_key(mutating_cmp))
+            def mutating_cmp(x, y):
+                L.append(3)
+                del L[:]
+                return (x > y) - (x < y)
+            self.assertRaises(ValueError, L.sort, key=cmp_to_key(mutating_cmp))
+            memorywaster = [memorywaster]
+
+#==============================================================================
+
+class TestDecorateSortUndecorate(unittest.TestCase):
+
+    def test_decorated(self):
+        data = 'The quick Brown fox Jumped over The lazy Dog'.split()
+        copy = data[:]
+        random.shuffle(data)
+        data.sort(key=str.lower)
+        def my_cmp(x, y):
+            xlower, ylower = x.lower(), y.lower()
+            return (xlower > ylower) - (xlower < ylower)
+        copy.sort(key=cmp_to_key(my_cmp))
+
+    def test_baddecorator(self):
+        data = 'The quick Brown fox Jumped over The lazy Dog'.split()
+        self.assertRaises(TypeError, data.sort, key=lambda x,y: 0)
+
+    def test_stability(self):
+        data = [(random.randrange(100), i) for i in range(200)]
+        copy = data[:]
+        data.sort(key=lambda t: t[0])   # sort on the random first field
+        copy.sort()                     # sort using both fields
+        self.assertEqual(data, copy)    # should get the same result
+
+    def test_key_with_exception(self):
+        # Verify that the wrapper has been removed
+        data = list(range(-2, 2))
+        dup = data[:]
+        self.assertRaises(ZeroDivisionError, data.sort, key=lambda x: 1/x)
+        self.assertEqual(data, dup)
+
+    def test_key_with_mutation(self):
+        data = list(range(10))
+        def k(x):
+            del data[:]
+            data[:] = range(20)
+            return x
+        self.assertRaises(ValueError, data.sort, key=k)
+
+    @unittest.skip("TODO: RUSTPYTHON; destructors")
+    def test_key_with_mutating_del(self):
+        data = list(range(10))
+        class SortKiller(object):
+            def __init__(self, x):
+                pass
+            def __del__(self):
+                del data[:]
+                data[:] = range(20)
+            def __lt__(self, other):
+                return id(self) < id(other)
+        self.assertRaises(ValueError, data.sort, key=SortKiller)
+
+    @unittest.skip("TODO: RUSTPYTHON; destructors")
+    def test_key_with_mutating_del_and_exception(self):
+        data = list(range(10))
+        ## dup = data[:]
+        class SortKiller(object):
+            def __init__(self, x):
+                if x > 2:
+                    raise RuntimeError
+            def __del__(self):
+                del data[:]
+                data[:] = list(range(20))
+        self.assertRaises(RuntimeError, data.sort, key=SortKiller)
+        ## major honking subtlety: we *can't* do:
+        ##
+        ## self.assertEqual(data, dup)
+        ##
+        ## because there is a reference to a SortKiller in the
+        ## traceback and by the time it dies we're outside the call to
+        ## .sort() and so the list protection gimmicks are out of
+        ## date (this cost some brain cells to figure out...).
+
+    def test_reverse(self):
+        data = list(range(100))
+        random.shuffle(data)
+        data.sort(reverse=True)
+        self.assertEqual(data, list(range(99,-1,-1)))
+
+    def test_reverse_stability(self):
+        data = [(random.randrange(100), i) for i in range(200)]
+        copy1 = data[:]
+        copy2 = data[:]
+        def my_cmp(x, y):
+            x0, y0 = x[0], y[0]
+            return (x0 > y0) - (x0 < y0)
+        def my_cmp_reversed(x, y):
+            x0, y0 = x[0], y[0]
+            return (y0 > x0) - (y0 < x0)
+        data.sort(key=cmp_to_key(my_cmp), reverse=True)
+        copy1.sort(key=cmp_to_key(my_cmp_reversed))
+        self.assertEqual(data, copy1)
+        copy2.sort(key=lambda x: x[0], reverse=True)
+        self.assertEqual(data, copy2)
+
+#==============================================================================
+def check_against_PyObject_RichCompareBool(self, L):
+    ## The idea here is to exploit the fact that unsafe_tuple_compare uses
+    ## PyObject_RichCompareBool for the second elements of tuples. So we have,
+    ## for (most) L, sorted(L) == [y[1] for y in sorted([(0,x) for x in L])]
+    ## This will work as long as __eq__ => not __lt__ for all the objects in L,
+    ## which holds for all the types used below.
+    ##
+    ## Testing this way ensures that the optimized implementation remains consistent
+    ## with the naive implementation, even if changes are made to any of the
+    ## richcompares.
+    ##
+    ## This function tests sorting for three lists (it randomly shuffles each one):
+    ##                        1. L
+    ##                        2. [(x,) for x in L]
+    ##                        3. [((x,),) for x in L]
+
+    random.seed(0)
+    random.shuffle(L)
+    L_1 = L[:]
+    L_2 = [(x,) for x in L]
+    L_3 = [((x,),) for x in L]
+    for L in [L_1, L_2, L_3]:
+        optimized = sorted(L)
+        reference = [y[1] for y in sorted([(0,x) for x in L])]
+        for (opt, ref) in zip(optimized, reference):
+            self.assertIs(opt, ref)
+            #note: not assertEqual! We want to ensure *identical* behavior.
+
+class TestOptimizedCompares(unittest.TestCase):
+    def test_safe_object_compare(self):
+        heterogeneous_lists = [[0, 'foo'],
+                               [0.0, 'foo'],
+                               [('foo',), 'foo']]
+        for L in heterogeneous_lists:
+            self.assertRaises(TypeError, L.sort)
+            self.assertRaises(TypeError, [(x,) for x in L].sort)
+            self.assertRaises(TypeError, [((x,),) for x in L].sort)
+
+        float_int_lists = [[1,1.1],
+                           [1<<70,1.1],
+                           [1.1,1],
+                           [1.1,1<<70]]
+        for L in float_int_lists:
+            check_against_PyObject_RichCompareBool(self, L)
+
+    # XXX RUSTPYTHON: added by us but it seems like an implementation detail
+    @support.cpython_only
+    def test_unsafe_object_compare(self):
+
+        # This test is by ppperry. It ensures that unsafe_object_compare is
+        # verifying ms->key_richcompare == tp->richcompare before comparing.
+
+        class WackyComparator(int):
+            def __lt__(self, other):
+                elem.__class__ = WackyList2
+                return int.__lt__(self, other)
+
+        class WackyList1(list):
+            pass
+
+        class WackyList2(list):
+            def __lt__(self, other):
+                raise ValueError
+
+        L = [WackyList1([WackyComparator(i), i]) for i in range(10)]
+        elem = L[-1]
+        with self.assertRaises(ValueError):
+            L.sort()
+
+        L = [WackyList1([WackyComparator(i), i]) for i in range(10)]
+        elem = L[-1]
+        with self.assertRaises(ValueError):
+            [(x,) for x in L].sort()
+
+        # The following test is also by ppperry. It ensures that
+        # unsafe_object_compare handles Py_NotImplemented appropriately.
+        class PointlessComparator:
+            def __lt__(self, other):
+                return NotImplemented
+        L = [PointlessComparator(), PointlessComparator()]
+        self.assertRaises(TypeError, L.sort)
+        self.assertRaises(TypeError, [(x,) for x in L].sort)
+
+        # The following tests go through various types that would trigger
+        # ms->key_compare = unsafe_object_compare
+        lists = [list(range(100)) + [(1<<70)],
+                 [str(x) for x in range(100)] + ['\uffff'],
+                 [bytes(x) for x in range(100)],
+                 [cmp_to_key(lambda x,y: x<y)(x) for x in range(100)]]
+        for L in lists:
+            check_against_PyObject_RichCompareBool(self, L)
+
+    def test_unsafe_latin_compare(self):
+        check_against_PyObject_RichCompareBool(self, [str(x) for
+                                                      x in range(100)])
+
+    def test_unsafe_long_compare(self):
+        check_against_PyObject_RichCompareBool(self, [x for
+                                                      x in range(100)])
+
+    def test_unsafe_float_compare(self):
+        check_against_PyObject_RichCompareBool(self, [float(x) for
+                                                      x in range(100)])
+
+    def test_unsafe_tuple_compare(self):
+        # This test was suggested by Tim Peters. It verifies that the tuple
+        # comparison respects the current tuple compare semantics, which do not
+        # guarantee that x < x <=> (x,) < (x,)
+        #
+        # Note that we don't have to put anything in tuples here, because
+        # the check function does a tuple test automatically.
+
+        check_against_PyObject_RichCompareBool(self, [float('nan')]*100)
+        check_against_PyObject_RichCompareBool(self, [float('nan') for
+                                                      _ in range(100)])
+
+    def test_not_all_tuples(self):
+        self.assertRaises(TypeError, [(1.0, 1.0), (False, "A"), 6].sort)
+        self.assertRaises(TypeError, [('a', 1), (1, 'a')].sort)
+        self.assertRaises(TypeError, [(1, 'a'), ('a', 1)].sort)
+#==============================================================================
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/vm/Cargo.toml b/vm/Cargo.toml
index 6f2d27f2e..2d43fc09d 100644
--- a/vm/Cargo.toml
+++ b/vm/Cargo.toml
@@ -76,6 +76,7 @@ crossbeam-utils = "0.7"
 parking_lot = "0.11"
 thread_local = "1.0"
 cfg-if = "0.1.10"
+timsort = "0.1"
 
 ## unicode stuff
 unicode_names2 = "0.4"
diff --git a/vm/src/builtins.rs b/vm/src/builtins.rs
index d5076e522..699210b3f 100644
--- a/vm/src/builtins.rs
+++ b/vm/src/builtins.rs
@@ -24,6 +24,7 @@ mod decl {
     use crate::obj::objfunction::PyFunctionRef;
     use crate::obj::objint::{self, PyIntRef};
     use crate::obj::objiter;
+    use crate::obj::objlist::{PyList, SortOptions};
     use crate::obj::objsequence;
     use crate::obj::objstr::{PyString, PyStringRef};
     use crate::obj::objtype::{self, PyClassRef};
@@ -162,14 +163,14 @@ mod decl {
     }
 
     #[pyfunction]
-    fn dir(obj: OptionalArg<PyObjectRef>, vm: &VirtualMachine) -> PyResult {
+    fn dir(obj: OptionalArg<PyObjectRef>, vm: &VirtualMachine) -> PyResult<PyList> {
         let seq = match obj {
             OptionalArg::Present(obj) => vm.call_method(&obj, "__dir__", vec![])?,
             OptionalArg::Missing => {
                 vm.call_method(&vm.get_locals().into_object(), "keys", vec![])?
             }
         };
-        let sorted = sorted(vm, PyFuncArgs::new(vec![seq], vec![]))?;
+        let sorted = sorted(seq, Default::default(), vm)?;
         Ok(sorted)
     }
 
@@ -452,41 +453,32 @@ mod decl {
             }
         };
 
-        if candidates.is_empty() {
-            return default
-                .ok_or_else(|| vm.new_value_error("max() arg is an empty sequence".to_owned()));
-        }
-
-        // Start with first assumption:
         let mut candidates_iter = candidates.into_iter();
-        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(ref f) = &key_func {
-            if vm.is_none(f) {
-                x.clone()
-            } else {
-                vm.invoke(f, vec![x.clone()])?
+        let mut x = match candidates_iter.next() {
+            Some(x) => x,
+            None => {
+                return default
+                    .ok_or_else(|| vm.new_value_error("max() arg is an empty sequence".to_owned()))
             }
-        } else {
-            x.clone()
         };
 
-        for y in candidates_iter {
-            let y_key = if let Some(ref f) = &key_func {
-                if vm.is_none(f) {
-                    y.clone()
-                } else {
-                    vm.invoke(f, vec![y.clone()])?
+        let key_func = key_func.filter(|f| !vm.is_none(f));
+        if let Some(ref key_func) = key_func {
+            let mut x_key = vm.invoke(key_func, x.clone())?;
+            for y in candidates_iter {
+                let y_key = vm.invoke(key_func, y.clone())?;
+                let y_gt_x = objbool::boolval(vm, vm._gt(y_key.clone(), x_key.clone())?)?;
+                if y_gt_x {
+                    x = y;
+                    x_key = y_key;
+                }
+            }
+        } else {
+            for y in candidates_iter {
+                let y_gt_x = objbool::boolval(vm, vm._gt(y.clone(), x.clone())?)?;
+                if y_gt_x {
+                    x = y;
                 }
-            } else {
-                y.clone()
-            };
-            let order = vm._gt(x_key.clone(), y_key.clone())?;
-
-            if !objbool::get_value(&order) {
-                x = y.clone();
-                x_key = y_key;
             }
         }
 
@@ -753,14 +745,10 @@ mod decl {
     // builtin_slice
 
     #[pyfunction]
-    fn sorted(vm: &VirtualMachine, mut args: PyFuncArgs) -> PyResult {
-        let iterable = args
-            .take_positional()
-            .ok_or_else(|| vm.new_type_error("sorted expected 1 arguments, got 0".to_string()))?;
+    fn sorted(iterable: PyObjectRef, opts: SortOptions, vm: &VirtualMachine) -> PyResult<PyList> {
         let items = vm.extract_elements(&iterable)?;
-        let lst = vm.ctx.new_list(items);
-
-        vm.call_method(&lst, "sort", args)?;
+        let lst = PyList::from(items);
+        lst.sort(opts, vm)?;
         Ok(lst)
     }
 
diff --git a/vm/src/obj/objlist.rs b/vm/src/obj/objlist.rs
index 8bcdfc596..fad440d0c 100644
--- a/vm/src/obj/objlist.rs
+++ b/vm/src/obj/objlist.rs
@@ -92,8 +92,8 @@ impl PyList {
     }
 }
 
-#[derive(FromArgs)]
-struct SortOptions {
+#[derive(FromArgs, Default)]
+pub(crate) struct SortOptions {
     #[pyarg(keyword_only, default = "None")]
     key: Option<PyObjectRef>,
     #[pyarg(keyword_only, default = "false")]
@@ -729,13 +729,14 @@ impl PyList {
     }
 
     #[pymethod]
-    fn sort(&self, options: SortOptions, vm: &VirtualMachine) -> PyResult<()> {
+    pub(crate) fn sort(&self, options: SortOptions, vm: &VirtualMachine) -> PyResult<()> {
         // replace list contents with [] for duration of sort.
         // this prevents keyfunc from messing with the list and makes it easy to
         // check if it tries to append elements to it.
         let mut elements = std::mem::take(self.borrow_value_mut().deref_mut());
-        do_sort(vm, &mut elements, options.key, options.reverse)?;
+        let res = do_sort(vm, &mut elements, options.key, options.reverse);
         std::mem::swap(self.borrow_value_mut().deref_mut(), &mut elements);
+        res?;
 
         if !elements.is_empty() {
             return Err(vm.new_value_error("list modified during sort".to_owned()));
@@ -760,66 +761,29 @@ impl PyList {
     }
 }
 
-fn quicksort(
-    vm: &VirtualMachine,
-    keys: &mut [PyObjectRef],
-    values: &mut [PyObjectRef],
-) -> PyResult<()> {
-    let len = values.len();
-    if len >= 2 {
-        let pivot = partition(vm, keys, values)?;
-        quicksort(vm, &mut keys[0..pivot], &mut values[0..pivot])?;
-        quicksort(vm, &mut keys[pivot + 1..len], &mut values[pivot + 1..len])?;
-    }
-    Ok(())
-}
-
-fn partition(
-    vm: &VirtualMachine,
-    keys: &mut [PyObjectRef],
-    values: &mut [PyObjectRef],
-) -> PyResult<usize> {
-    let len = values.len();
-    let pivot = len / 2;
-
-    values.swap(pivot, len - 1);
-    keys.swap(pivot, len - 1);
-
-    let mut store_idx = 0;
-    for i in 0..len - 1 {
-        let result = vm._lt(keys[i].clone(), keys[len - 1].clone())?;
-        let boolval = objbool::boolval(vm, result)?;
-        if boolval {
-            values.swap(i, store_idx);
-            keys.swap(i, store_idx);
-            store_idx += 1;
-        }
-    }
-
-    values.swap(store_idx, len - 1);
-    keys.swap(store_idx, len - 1);
-    Ok(store_idx)
-}
-
 fn do_sort(
     vm: &VirtualMachine,
     values: &mut Vec<PyObjectRef>,
     key_func: Option<PyObjectRef>,
     reverse: bool,
 ) -> PyResult<()> {
-    // build a list of keys. If no keyfunc is provided, it's a copy of the list.
-    let mut keys: Vec<PyObjectRef> = vec![];
-    for x in values.iter() {
-        keys.push(match &key_func {
-            None => x.clone(),
-            Some(ref func) => vm.invoke(func, vec![x.clone()])?,
-        });
-    }
+    let cmp = if reverse {
+        VirtualMachine::_lt
+    } else {
+        VirtualMachine::_gt
+    };
+    let cmp =
+        |a: &PyObjectRef, b: &PyObjectRef| objbool::boolval(vm, cmp(vm, a.clone(), b.clone())?);
 
-    quicksort(vm, &mut keys, values)?;
-
-    if reverse {
-        values.reverse();
+    if let Some(ref key_func) = key_func {
+        let mut items = values
+            .iter()
+            .map(|x| Ok((x.clone(), vm.invoke(key_func, vec![x.clone()])?)))
+            .collect::<Result<Vec<_>, _>>()?;
+        timsort::try_sort_by_gt(&mut items, |a, b| cmp(&a.1, &b.1))?;
+        *values = items.into_iter().map(|(val, _)| val).collect();
+    } else {
+        timsort::try_sort_by_gt(values, cmp)?;
     }
 
     Ok(())
diff --git a/vm/src/stdlib/random.rs b/vm/src/stdlib/random.rs
index aab9e6909..77193ec06 100644
--- a/vm/src/stdlib/random.rs
+++ b/vm/src/stdlib/random.rs
@@ -91,7 +91,8 @@ mod _random {
                     if cfg!(target_endian = "big") {
                         key.reverse();
                     }
-                    PyRng::MT(Box::new(mt19937::MT19937::new_with_slice_seed(&key)))
+                    let key = if key.is_empty() { &[0] } else { key.as_slice() };
+                    PyRng::MT(Box::new(mt19937::MT19937::new_with_slice_seed(key)))
                 }
             };