diff --git a/README.md b/README.md index b8c28aadf..9dcb647b4 100644 --- a/README.md +++ b/README.md @@ -72,6 +72,13 @@ cargo build --release --target wasm32-wasi --features="freeze-stdlib" > Note: we use the `freeze-stdlib` to include the standard library inside the binary. + +## Embedding RustPython into your Rust Applications + +Interested in exposing Python scripting in an application written in Rust, +perhaps to allow quickly tweaking logic where Rust's compile times would be inhibitive? +Then `examples/hello_embed.rs` and `examples/mini_repl.rs` may be of some assistance. + ## Disclaimer RustPython is in a development phase and should not be used in production or a diff --git a/examples/hello_embed.rs b/examples/hello_embed.rs new file mode 100644 index 000000000..7db217483 --- /dev/null +++ b/examples/hello_embed.rs @@ -0,0 +1,20 @@ +use rustpython_compiler as compiler; +use rustpython_vm as vm; + +fn main() -> vm::pyobject::PyResult<()> { + let vm = vm::VirtualMachine::new(vm::PySettings::default()); + + let scope = vm.new_scope_with_builtins(); + + let code_obj = vm + .compile( + r#"print("Hello World!")"#, + compiler::compile::Mode::Exec, + "".to_string(), + ) + .map_err(|err| vm.new_syntax_error(&err))?; + + vm.run_code_obj(code_obj, scope)?; + + Ok(()) +} diff --git a/examples/mini_repl.rs b/examples/mini_repl.rs new file mode 100644 index 000000000..7a7da6088 --- /dev/null +++ b/examples/mini_repl.rs @@ -0,0 +1,117 @@ +///! This example show cases a very simple REPL. +///! While a much better REPL can be found in ../src/shell, +///! This much smaller REPL is still a useful example because it showcases inserting +///! values and functions into the Python runtime's scope, and showcases use +///! of the compilation mode "Single". +use rustpython_compiler as compiler; +use rustpython_vm as vm; +// these are needed for special memory shenanigans to let us share a variable with Python and Rust +use std::cell::Cell; +use std::rc::Rc; +// this needs to be in scope in order to insert things into scope.globals +use vm::pyobject::ItemProtocol; + +// This has to be a macro because it uses the py_compile_bytecode macro, +// which compiles python source to optimized bytecode at compile time, so that +// the program you're embedding this into doesn't take longer to start up. +macro_rules! add_python_function { + ( $scope:ident, $vm:ident, $src:literal $(,)? ) => {{ + // this has to be in scope to turn a PyValue into a PyRef + // (a PyRef is a special reference that points to something in the VirtualMachine) + use vm::pyobject::PyValue; + + // you can safely assume that only one module will be created when passing a source literal + // to py_compile_bytecode. However, it is also possible to pass directories, which may + // return more modules. + let (_, vm::bytecode::FrozenModule { code, .. }): (String, _) = + vm::py_compile_bytecode!(source = $src) + .into_iter() + .collect::>() + .pop() + .expect("No modules found in the provided source!"); + + // takes the first constant in the file that's a function + let def = code + .get_constants() + .find_map(|c| match c { + vm::bytecode::Constant::Code { code } => Some(code), + _ => None, + }) + .expect("No functions found in the provided module!"); + + // inserts the first function found in the module into the provided scope. + $scope.globals.set_item( + &def.obj_name, + $vm.context().new_pyfunction( + vm::obj::objcode::PyCode::new(*def.clone()).into_ref(&$vm), + $scope.clone(), + None, + None, + ), + &$vm, + ) + }}; +} + +fn main() -> vm::pyobject::PyResult<()> { + // you can also use a raw pointer instead of Rc>, but that requires usage of unsafe. + // both methods are ways of circumnavigating the fact that Python doesn't respect Rust's borrow + // checking rules. + let on: Rc> = Rc::new(Cell::new(true)); + + let mut input = String::with_capacity(50); + let stdin = std::io::stdin(); + + let vm = vm::VirtualMachine::new(vm::PySettings::default()); + let scope: vm::scope::Scope = vm.new_scope_with_builtins(); + + // typing `quit()` is too long, let's make `on(False)` work instead. + scope.globals.set_item( + "on", + vm.context().new_function({ + let on = Rc::clone(&on); + move |b: bool| on.set(b) + }), + &vm, + )?; + + // let's include a fibonacci function, but let's be lazy and write it in Python + add_python_function!( + scope, + vm, + // a fun line to test this with is + // ''.join( l * fib(i) for i, l in enumerate('supercalifragilistic') ) + r#"def fib(n): return n if n <= 1 else fib(n - 1) + fib(n - 2)"# + )?; + + while on.get() { + input.clear(); + stdin + .read_line(&mut input) + .expect("Failed to read line of input"); + + // this line also automatically prints the output + // (note that this is only the case when compile::Mode::Single is passed to vm.compile) + match vm + .compile( + &input, + compiler::compile::Mode::Single, + "".to_string(), + ) + .map_err(|err| vm.new_syntax_error(&err)) + .and_then(|code_obj| vm.run_code_obj(code_obj, scope.clone())) + { + Ok(output) => { + // store the last value in the "last" variable + if !vm.is_none(&output) { + scope.globals.set_item("last", output, &vm)?; + } + } + Err(e) => { + vm::exceptions::print_exception(&vm, &e); + } + } + } + + Ok(()) +}