# RustPython

A Python-3 (CPython >= 3.5.0) Interpreter written in Rust :snake: :scream: :metal:.

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# Usage

### Check out our [online demo](https://rustpython.github.io/demo/) running on WebAssembly.

To test RustPython, do the following:

    $ git clone https://github.com/RustPython/RustPython
    $ cd RustPython
    $ cargo run demo.py
    Hello, RustPython!

Or use the interactive shell:

    $ cargo run
    Welcome to rustpython
    >>>>> 2+2
    4

# Disclaimer

  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. 

# Goals

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

# Documentation

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

You can read the [online documentation](https://rustpython.github.io/website/rustpython/index.html) for the latest code on master.

You can also generate documentation locally by running:

```shell
$ 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
  - `builtins.rs`: Builtin functions
  - `compile.rs`: 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

# Contributing

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](https://github.com/RustPython/RustPython/issues).
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/whats_left_to_implement.py` to assist in finding any
unimplemented method.

# Testing

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

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

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

```shell
$ 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](https://github.com/pybee/ouroboros).

To do this, follow this method:

```shell
$ cd ~/GIT
$ git clone git@github.com:pybee/ouroboros.git
$ 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.

## Setup

To get started, install [wasm-pack](https://rustwasm.github.io/wasm-pack/installer/) and `npm`. ([wasm-bindgen](https://rustwasm.github.io/wasm-bindgen/whirlwind-tour/basic-usage.html) should be installed by `wasm-pack`. if not, install it yourself)

<!-- Using `rustup` add the compile target `wasm32-unknown-emscripten`. To do so you will need to have [rustup](https://rustup.rs/) installed.

```bash
rustup target add wasm32-unknown-emscripten
```

Next, install `emsdk`:

```bash
curl https://s3.amazonaws.com/mozilla-games/emscripten/releases/emsdk-portable.tar.gz | tar -zxv
cd emsdk-portable/
./emsdk update
./emsdk install sdk-incoming-64bit
./emsdk activate sdk-incoming-64bit
``` -->

## Build

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
https://rustpython.github.io/demo in `wasm/demo`, and an example of how to use
the crate as a library in one's own JS app in `wasm/example`.

```sh
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.

```sh
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.

```sh
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:

```js
rp.pyEval(
  `
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.

# Community

Chat with us on [gitter][gitter].

# Credit

The initial work was based on [windelbouwman/rspython](https://github.com/windelbouwman/rspython) and [shinglyu/RustPython](https://github.com/shinglyu/RustPython)

[gitter]: https://gitter.im/rustpython/Lobby

# Links

These are some useful links to related projects:

- https://github.com/ProgVal/pythonvm-rust
- https://github.com/shinglyu/RustPython
- https://github.com/windelbouwman/rspython