PyO3

Rust bindings for Python, including tools for creating native Python extension modules. Running and interacting with Python code from a Rust binary is also supported.

• User Guide: stable | main

• API Documentation: stable | main

Usage

Requires Rust 1.83 or greater.

PyO3 supports the following Python distributions:

• CPython 3.8 or greater
• PyPy 7.3 (Python 3.11+)
• GraalPy 25.0 or greater (Python 3.12+)

You can use PyO3 to write a native Python module in Rust, or to embed Python in a Rust binary. The following sections explain each of these in turn.

Using Rust from Python

PyO3 can be used to generate a native Python module. The easiest way to try this out for the first time is to use maturin. maturin is a tool for building and publishing Rust-based Python packages with minimal configuration. The following steps install maturin, use it to generate and build a new Python package, and then launch Python to import and execute a function from the package.

First, follow the commands below to create a new directory containing a new Python virtualenv, and install maturin into the virtualenv using Python's package manager, pip:

# (replace string_sum with the desired package name)
$ mkdir string_sum
$ cd string_sum
$ python -m venv .env
$ source .env/bin/activate
$ pip install maturin

Still inside this string_sum directory, now run maturin init. This will generate the new package source. When given the choice of bindings to use, select pyo3 bindings:

$ maturin init
✔ 🤷 What kind of bindings to use? · pyo3
  ✨ Done! New project created string_sum

The most important files generated by this command are Cargo.toml and lib.rs, which will look roughly like the following:

Cargo.toml

[package]
name = "string_sum"
version = "0.1.0"
edition = "2021"

[lib]
# The name of the native library. This is the name which will be used in Python to import the
# library (i.e. `import string_sum`). If you change this, you must also change the name of the
# `#[pymodule]` in `src/lib.rs`.
name = "string_sum"
# "cdylib" is necessary to produce a shared library for Python to import from.
#
# Downstream Rust code (including code in `bin/`, `examples/`, and `tests/`) will not be able
# to `use string_sum;` unless the "rlib" or "lib" crate type is also included, e.g.:
# crate-type = ["cdylib", "rlib"]
crate-type = ["cdylib"]

[dependencies]
pyo3 = "0.28.2"

src/lib.rs

/// A Python module implemented in Rust. The name of this module must match
/// the `lib.name` setting in the `Cargo.toml`, else Python will not be able to
/// import the module.
#[pyo3::pymodule]
mod string_sum {
  use pyo3::prelude::*;

  /// Formats the sum of two numbers as string.
  #[pyfunction]
  fn sum_as_string(a: usize, b: usize) -> PyResult<String> {
    Ok((a + b).to_string())
  }
}

Finally, run maturin develop. This will build the package and install it into the Python virtualenv previously created and activated. The package is then ready to be used from python:

$ maturin develop
# lots of progress output as maturin runs the compilation...
$ python
>>> import string_sum
>>> string_sum.sum_as_string(5, 20)
'25'

To make changes to the package, just edit the Rust source code and then re-run maturin develop to recompile.

To run this all as a single copy-and-paste, use the bash script below (replace string_sum in the first command with the desired package name):

mkdir string_sum && cd "$_"
python -m venv .env
source .env/bin/activate
pip install maturin
maturin init --bindings pyo3
maturin develop

If you want to be able to run cargo test or use this project in a Cargo workspace and are running into linker issues, there are some workarounds in the FAQ.

As well as with maturin, it is possible to build using setuptools-rust or manually. Both offer more flexibility than maturin but require more configuration to get started.

Using Python from Rust

To embed Python into a Rust binary, you need to ensure that your Python installation contains a shared library. The following steps demonstrate how to ensure this (for Ubuntu), and then give some example code which runs an embedded Python interpreter.

To install the Python shared library on Ubuntu:

sudo apt install python3-dev

To install the Python shared library on RPM based distributions (e.g. Fedora, Red Hat, SuSE), install the python3-devel package.

Start a new project with cargo new and add pyo3 to the Cargo.toml like this:

[dependencies.pyo3]
version = "0.28.2"
# Enabling this cargo feature will cause PyO3 to start a Python interpreter on first call to `Python::attach`
features = ["auto-initialize"]

Example program displaying the value of sys.version and the current user name:

use pyo3::prelude::*;
use pyo3::types::IntoPyDict;

fn main() -> PyResult<()> {
    Python::attach(|py| {
        let sys = py.import("sys")?;
        let version: String = sys.getattr("version")?.extract()?;

        let locals = [("os", py.import("os")?)].into_py_dict(py)?;
        let code = c"os.getenv('USER') or os.getenv('USERNAME') or 'Unknown'";
        let user: String = py.eval(code, None, Some(&locals))?.extract()?;

        println!("Hello {}, I'm Python {}", user, version);
        Ok(())
    })
}

The guide has a section with lots of examples about this topic.

Tools and libraries

• maturin Build and publish crates with pyo3, rust-cpython or cffi bindings as well as rust binaries as python packages
• setuptools-rust Setuptools plugin for Rust support.
• pyo3-built Simple macro to expose metadata obtained with the built crate as a PyDict
• rust-numpy Rust binding of NumPy C-API
• dict-derive Derive FromPyObject to automatically transform Python dicts into Rust structs
• pyo3-log Bridge from Rust to Python logging
• pythonize Serde serializer for converting Rust objects to JSON-compatible Python objects
• pyo3-async-runtimes Utilities for interoperability with Python's Asyncio library and Rust's async runtimes.
• rustimport Directly import Rust files or crates from Python, without manual compilation step. Provides pyo3 integration by default and generates pyo3 binding code automatically.
• pyo3-arrow Lightweight Apache Arrow integration for pyo3.
• pyo3-bytes Integration between bytes and pyo3.
• pyo3-object_store Integration between object_store and pyo3.

Examples

• anise A modern, high-performance toolkit for spacecraft mission design, notably used to help softly land Firefly Blue Ghost on the Moon on 02 Feb 2025.
• arro3 A minimal Python library for Apache Arrow, connecting to the Rust arrow crate.
  • arro3-compute arro3-compute
  • arro3-core arro3-core
  • arro3-io arro3-io
• bed-reader Read and write the PLINK BED format, simply and efficiently.
  • Shows Rayon/ndarray::parallel (including capturing errors, controlling thread num), Python types to Rust generics, Github Actions
• blake3-py Python bindings for the BLAKE3 cryptographic hash function.
  • Parallelized builds on GitHub Actions for MacOS, Linux, Windows, including free-threaded 3.13t wheels.
• cellular_raza _A cellular agent-based simulation framework for building complex models from a