* Leave Rust-only name decoration out of a generated signature A leading underscore marks an argument Rust sees as unused and `r#` escapes a Rust keyword. Neither describes the parameter a Python caller passes, and `r#` is not valid Python, so `inspect.signature()` rejects any signature carrying one. Reporting the bare name fixes _sre.template, select.epoll.__exit__ and bytearray.__reduce_ex__ without touching them, and lets a method name a parameter after a Rust keyword. A parameter CPython itself names with a leading underscore, such as compile's `_feature_version`, reaches Python through a FromArgs field, which this never sees. Assisted-by: Claude Code:claude-opus-5 * Name builtin type parameters the way CPython names them A generated __text_signature__ reports the Rust parameter name, so a name chosen for Rust reaches anyone reading help() or inspect. Rename the ones CPython describes differently: list.pop's `i` becomes `index`, list.count's `needle` becomes `value`, __format__'s `spec` becomes `format_spec`, bytes.strip's `chars` becomes `bytes`, and object.__reduce_ex__'s `proto` becomes `protocol`. Left alone are the parameters CPython reports as `object` or `unused`. Those are synthesised from the METH_* flags rather than named: CPython reports slice.indices as ($self, object, /) while its own docstring calls the argument len. Assisted-by: Claude Code:claude-opus-5 * Name os parameters the way CPython names them os.read's `n` becomes `length`, os.lseek's `how` becomes `whence`, os.kill's `sig` becomes `signal`, os.stat's `file` becomes `path`, and os.putenv's `key` becomes `name`, among others. os.chmod is left alone. It reports (path, dir_fd, mode, follow_symlinks) while the call binds mode second and takes follow_symlinks by keyword, so the order and the kind are wrong rather than the names, which a rename cannot fix. os.fstatvfs is left alone too: it shares one Rust function with statvfs, which CPython names `path`, so the two aliases cannot report different names. Assisted-by: Claude Code:claude-opus-5 * Name sys parameters the way CPython names them sys.excepthook's (exc_type, exc_val, exc_tb) become (exctype, value, traceback), sys._getframe's `offset` becomes `depth`, sys.intern's `s` becomes `string`, and sys.settrace's `tracefunc` becomes `function`. sys._clear_type_descriptors takes the name CPython gives it, which Rust spells r#type. Assisted-by: Claude Code:claude-opus-5 * Name vm stdlib parameters the way CPython names them deque.rotate's `mid` becomes `n`, deque.extend's `iter` becomes `iterable`, _sre.ascii_tolower's `ch` becomes `character`, _operator.neg's `pos` becomes `a`, signal.alarm's `time` becomes `seconds`, and codecs.register_error's `name` becomes `errors`. gc.collect and charmap_build keep theirs. Their argument is a FromArgs struct or a PosArgs bundle, so the reported name is the binding rather than a parameter, and renaming the binding would only disguise that. Assisted-by: Claude Code:claude-opus-5 * Name stdlib crate parameters the way CPython names them unicodedata.category's `character` becomes `chr`, math.isqrt's `x` becomes `n`, cmath.polar's `x` becomes `z`, struct.calcsize's `fmt` becomes `format`, binascii.crc32's `init` becomes `crc`, zlib.adler32's `begin_state` becomes `value`, and array.append's `x` becomes `v`. array.fromunicode's parameter is `ustr`, which cspell has to be told about. array.__deepcopy__ keeps `_memo`, which the generator now reports as `memo`; CPython calls it `unused`, a name synthesised from METH_O rather than chosen. Assisted-by: Claude Code:claude-opus-5 * Name BaseExceptionGroup.split's parameter the way CPython names it CPython calls the argument of split and subgroup `matcher_value`. Assisted-by: Claude Code:claude-opus-5 * Strip a generated parameter name with unraw and one prefix check syn already removes r# through IdentExt::unraw, the way from_args.rs does for a field name. The empty-name guard never ran: a bare `_` is Pat::Wild, which func_sig has already refused. Assisted-by: Claude Code:claude-fable-5-1 * Take object and unused from CPython's Clinic signatures CPython also falls back to these names for METH_O, but list.append and insert, set.add, discard and remove, _weakref.getweakrefcount and getweakrefs, sys.displayhook and getrefcount, and array.__deepcopy__ get them from an Argument Clinic signature. The earlier commit that kept array.__deepcopy__'s `_memo` was wrong to call `unused` synthesised. test_pydoc's set.add summary-line tests now pass. Assisted-by: Claude Code:claude-opus-5
RustPython
A Python-3 (CPython >= 3.14.0) Interpreter written in Rust 🐍 😱 🤘.
Usage
Check out our online demo running on WebAssembly.
RustPython requires Rust latest stable version (e.g 1.67.1 at February 7th 2023). If you don't currently have Rust installed on your system you can do so by following the instructions at rustup.rs.
To check the version of Rust you're currently running, use rustc --version. If you wish to update,
rustup update stable will update your Rust installation to the most recent stable release.
To build RustPython locally, first, clone the source code:
git clone https://github.com/RustPython/RustPython
RustPython uses symlinks to manage python libraries in Lib/. If on windows, running the following helps:
git config core.symlinks true
Then you can change into the RustPython directory and run the demo (Note: --release is
needed to prevent stack overflow on Windows):
$ cd RustPython
$ cargo run --release -- -c 'print("Hello, RustPython!")'
Hello, RustPython!
Or use the interactive shell:
$ cargo run --release
Welcome to rustpython
>>>>> 2+2
4
NOTE: For windows users, please set RUSTPYTHONPATH environment variable as Lib path in project directory.
(e.g. When RustPython directory is C:\RustPython, set RUSTPYTHONPATH as C:\RustPython\Lib)
You can also install and run RustPython with the following:
$ cargo install --git https://github.com/RustPython/RustPython rustpython
$ rustpython
Welcome to the magnificent Rust Python interpreter
>>>>>
venv
Because RustPython currently doesn't provide a well-packaged installation, using venv helps to use pip easier.
$ rustpython -m venv <your_env_name>
$ . <your_env_name>/bin/activate
$ python # now `python` is the alias of the RustPython for the new env
PIP
If you'd like to make https requests, you can enable the ssl feature, which
also lets you install the pip package manager. Note that on Windows, you may
need to install OpenSSL, or you can enable the ssl-openssl-vendor feature instead,
which compiles OpenSSL for you but requires a C compiler, perl, and make.
OpenSSL version 3 is expected and tested in CI. Older versions may not work.
Once you've installed rustpython with SSL support, you can install pip by running:
cargo install --git https://github.com/RustPython/RustPython
rustpython --install-pip
You can also install RustPython through the conda package manager, though
this isn't officially supported and may be out of date:
conda install rustpython -c conda-forge
rustpython
SSL provider
For HTTPS requests, ssl-rustls-aws-lc is enabled by default for the RustPython binary. Embedders can use rustpython-stdlib's provider-agnostic ssl-rustls feature and install their own rustls crypto provider, or replace rustls with ssl-openssl if their environment requires OpenSSL.
Note that to use OpenSSL on Windows, you may need to install OpenSSL, or you can enable the ssl-openssl-vendor feature instead,
which compiles OpenSSL for you but requires a C compiler, perl, and make.
OpenSSL version 3 is expected and tested in CI. Older versions may not work.
WASI
You can compile RustPython to a standalone WebAssembly WASI module so it can run anywhere.
Build
cargo build --target wasm32-wasip1 --no-default-features --features freeze-stdlib,stdlib --release
Run by wasmer
wasmer run --volume `pwd` -- target/wasm32-wasip1/release/rustpython.wasm `pwd`/extra_tests/snippets/stdlib_random.py
Run by wapm
$ wapm install rustpython
$ wapm run rustpython
>>>>> 2+2
4
Building the WASI file
You can build the WebAssembly WASI file with:
cargo build --release --target wasm32-wasip1 --features="freeze-stdlib"
Note: we use the
freeze-stdlibto include the standard library inside the binary. You also have to run oncerustup target add wasm32-wasip1.
JIT (Just in time) compiler
RustPython has a very experimental JIT compiler that compile python functions into native code.
Building
By default the JIT compiler isn't enabled, it's enabled with the jit cargo feature.
cargo run --features jit
This requires autoconf, automake, libtool, and clang to be installed.
Using
To compile a function, call __jit__() on it.
def foo():
a = 5
return 10 + a
foo.__jit__() # this will compile foo to native code and subsequent calls will execute that native code
assert foo() == 15
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 development, and while the interpreter certainly can be used in interesting use cases like running Python in WASM and embedding into a Rust project, do note that RustPython is not totally production-ready.
Contribution is more than welcome! See our contribution section for more information on this.
Conference videos
Checkout those talks on conferences:
Use cases
Although RustPython is a fairly young project, a few people have used it to make cool projects:
- GreptimeDB: an open-source, cloud-native, distributed time-series database. Using RustPython for embedded scripting.
- pyckitup: a game engine written in rust.
- Robot Rumble: an arena-based AI competition platform
- Ruff: an extremely fast Python linter, written in Rust
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 for the latest release, or the user guide.
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 or you can append --open to the previous commands to
have the documentation open automatically on your default browser.
For a high level overview of the components, see the architecture document.
Contributing
Contributions are welcome and highly appreciated. To get started, check out the contributing guidelines.
You can also join us on Discord.
Compiling to WebAssembly
Community
Chat with us on Discord.
Code of conduct
Our code of conduct can be found here.
Credit
The initial work was based on windelbouwman/rspython and shinglyu/RustPython
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
License
This project is licensed under the MIT license. Please see the LICENSE file for more details.
The project logo is licensed under the CC-BY-4.0 license. Please see the LICENSE-logo file for more details.

