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A Python Interpreter written in Rust
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A Python-3 (CPython >= 3.5.0) Interpreter written in Rust 🐍 😱 🤘.

Build Status Build Status codecov License: MIT Contributors Gitter


Check out our online demo running on WebAssembly.

To test RustPython, do the following:

$ git clone
$ cd RustPython
$ cargo run
Hello, RustPython!

Or use the interactive shell:

$ cargo run
Welcome to rustpython
>>>>> 2+2


RustPython is in a development phase and should not be used in production or a fault intolerant setting.

Our current build supports only a subset of Python syntax.

Contribution is also more than welcome! See our contribution section for more information on this.


  • Full Python-3 environment entirely in Rust (not CPython bindings)
  • A clean implementation without compatibility hacks


Currently along with other areas of the project, documentation is still in an early phase.

You can read the online documentation for the latest code on master.

You can also generate documentation locally by running:

$ cargo doc # Including documentation for all dependencies
$ cargo doc --no-deps --all # Excluding all dependencies

Documentation HTML files can then be found in the target/doc directory.

If you wish to update the online documentation, push directly to the release branch (or ask a maintainer to do so). This will trigger a Travis build that updates the documentation and WebAssembly demo page.

Code organization

  • parser/src: python lexing, parsing and ast
  • vm/src: python virtual machine
    • Builtin functions
    • the python compiler from ast to bytecode
    • obj: python builtin types
  • src: using the other subcrates to bring rustpython to life.
  • docs: documentation (work in progress)
  • py_code_object: CPython bytecode to rustpython bytecode converter (work in progress)
  • wasm: Binary crate and resources for WebAssembly build
  • tests: integration test snippets


Contributions are more than welcome, and in many cases we are happy to guide contributors through PRs or on gitter.

With that in mind, please note this project is maintained by volunteers, some of the best ways to get started are below:

Most tasks are listed in the issue tracker. Check issues labeled with good first issue if you wish to start coding.

Another approach is to checkout the source code: builtin functions and object methods are often the simplest and easiest way to contribute.

You can also simply run cargo run tests/snippets/ to assist in finding any unimplemented method.


To test rustpython, there is a collection of python snippets located in the tests/snippets directory. To run those tests do the following:

$ cd tests
$ pipenv install
$ pipenv run pytest -v

There also are some unit tests, you can run those with cargo:

$ cargo test --all

Using another standard library

As of now the standard library is under construction.

You can play around with other standard libraries for python. For example, the ouroboros library.

To do this, follow this method:

$ cd ~/GIT
$ git clone
$ export PYTHONPATH=~/GIT/ouroboros/ouroboros
$ cd RustPython
$ cargo run -- -c 'import statistics'

Compiling to WebAssembly

At this stage RustPython only has preliminary support for web assembly. The instructions here are intended for developers or those wishing to run a toy example.


To get started, install wasm-pack and npm. (wasm-bindgen should be installed by wasm-pack. if not, install it yourself)


Move into the wasm directory. This directory contains a library crate for interop with python to rust to js and back in wasm/lib, the demo website found at in wasm/demo, and an example of how to use the crate as a library in one's own JS app in wasm/example.

cd wasm

Go to the demo directory. This is the best way of seeing the changes made to either the library or the JS demo, as the rustpython_wasm module is set to the global JS variable rp on the website.

cd demo

Now, start the webpack development server. It'll compile the crate and then the demo app. This will likely take a long time, both the wasm-pack portion and the webpack portion (from after it says "Your crate has been correctly compiled"), so be patient.

npm run dev

You can now open the webpage on https://localhost:8080 and Python code in either the text box or browser devtools with:

print(js_vars['a'] * 9)
    vars: {
      a: 9

Alternatively, you can run npm run build to build the app once, without watching for changes, or npm run dist to build the app in release mode, both for the crate and webpack.

Code style

The code style used is the default rustfmt codestyle. Please format your code accordingly.


Chat with us on gitter.

Code of conduct

Our code of conduct can be found here.


The initial work was based on windelbouwman/rspython and shinglyu/RustPython


These are some useful links to related projects:

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