Maturin

formerly pyo3-pack

Build and publish crates with pyo3, rust-cpython and cffi bindings as well as rust binaries as python packages.

This project is meant as a zero configuration replacement for setuptools-rust and milksnake. It supports building wheels for python 3.5+ on windows, linux, mac and freebsd, can upload them to pypi and has basic pypy support.

Check out the User Guide!

Usage

You can either download binaries from the latest release or install it with pip:

pip install maturin

There are four main commands:

maturin new creates a new cargo project with maturin configured.
maturin publish builds the crate into python packages and publishes them to pypi.
maturin build builds the wheels and stores them in a folder (target/wheels by default), but doesn't upload them. It's possible to upload those with twine or maturin upload.
maturin develop builds the crate and installs it as a python module directly in the current virtualenv. Note that while maturin develop is faster, it doesn't support all the feature that running pip install after maturin build supports.

pyo3 and rust-cpython bindings are automatically detected, for cffi or binaries you need to pass -b cffi or -b bin. maturin doesn't need extra configuration files and doesn't clash with an existing setuptools-rust or milksnake configuration. You can even integrate it with testing tools such as tox. There are examples for the different bindings in the test-crates folder.

The name of the package will be the name of the cargo project, i.e. the name field in the [package] section of Cargo.toml. The name of the module, which you are using when importing, will be the name value in the [lib] section (which defaults to the name of the package). For binaries, it's simply the name of the binary generated by cargo.

Python packaging basics

Python packages come in two formats: A built form called wheel and source distributions (sdist), both of which are archives. A wheel can be compatible with any python version, interpreter (cpython and pypy, mainly), operating system and hardware architecture (for pure python wheels), can be limited to a specific platform and architecture (e.g. when using ctypes or cffi) or to a specific python interpreter and version on a specific architecture and operating system (e.g. with pyo3 and rust-cpython).

When using pip install on a package, pip tries to find a matching wheel and install that. If it doesn't find one, it downloads the source distribution and builds a wheel for the current platform, which requires the right compilers to be installed. Installing a wheel is much faster than installing a source distribution as building wheels is generally slow.

When you publish a package to be installable with pip install, you upload it to pypi, the official package repository. For testing, you can use test pypi instead, which you can use with pip install --index-url https://test.pypi.org/simple/. Note that for publishing for linux, you need to use the manylinux docker container, while for publishing from your repository you can use the messense/maturin-action github action.

pyo3 and rust-cpython

For pyo3 and rust-cpython, maturin can only build packages for installed python versions. On linux and mac, all python versions in PATH are used. If you don't set your own interpreters with -i, a heuristic is used to search for python installations. On windows all versions from the python launcher (which is installed by default by the python.org installer) and all conda environments except base are used. You can check which versions are picked up with the list-python subcommand.

pyo3 will set the used python interpreter in the environment variable PYTHON_SYS_EXECUTABLE, which can be used from custom build scripts. Maturin can build and upload wheels for pypy with pyo3, even though only pypy3.7-7.3 on linux is tested.

Cffi

Cffi wheels are compatible with all python versions including pypy. If cffi isn't installed and python is running inside a virtualenv, maturin will install it, otherwise you have to install it yourself (pip install cffi).

maturin uses cbindgen to generate a header file, which can be customized by configuring cbindgen through a cbindgen.toml file inside your project root. Alternatively you can use a build script that writes a header file to $PROJECT_ROOT/target/header.h.

Based on the header file maturin generates a module which exports an ffi and a lib object.

Example of a custom build script

use cbindgen;
use std::env;
use std::path::Path;

fn main() {
    let crate_dir = env::var("CARGO_MANIFEST_DIR").unwrap();

    let bindings = cbindgen::Builder::new()
        .with_no_includes()
        .with_language(cbindgen::Language::C)
        .with_crate(crate_dir)
        .generate()
        .unwrap();
    bindings.write_to_file(Path::new("target").join("header.h"));
}

Mixed rust/python projects

To create a mixed rust/python project, create a folder with your module name (i.e. lib.name in Cargo.toml) next to your Cargo.toml and add your python sources there:

my-project
├── Cargo.toml
├── my_project
│   ├── __init__.py
│   └── bar.py
├── pyproject.toml
├── Readme.md
└── src
    └── lib.rs

You can specify a different python source directory in Cargo.toml by setting package.metadata.maturin.python-source, for example

[package.metadata.maturin]
python-source = "python"

then the project structure would look like this:

my-project
├── Cargo.toml
├── python
│   └── my_project
│       ├── __init__.py
│       └── bar.py
├── pyproject.toml
├── Readme.md
└── src
    └── lib.rs

maturin will add the native extension as a module in your python folder. When using develop, maturin will copy the native library and for cffi also the glue code to your python folder. You should add those files to your gitignore.

With cffi you can do from .my_project import lib and then use lib.my_native_function, with pyo3/rust-cpython you can directly from .my_project import my_native_function.

Example layout with pyo3 after maturin develop:

my-project
├── Cargo.toml
├── my_project
│   ├── __init__.py
│   ├── bar.py
│   └── my_project.cpython-36m-x86_64-linux-gnu.so
├── Readme.md
└── src
    └── lib.rs

Python metadata

maturin supports PEP 621, you can specify python package metadata in pyproject.toml. maturin merges metadata from Cargo.toml and pyproject.toml, pyproject.toml take precedence over Cargo.toml.

To specify python dependencies, add a list dependencies in a [project] section in the pyproject.toml. This list is equivalent to install_requires in setuptools:

[project]
name = "my-project"
dependencies = ["flask~=1.1.0", "toml==0.10.0"]

Pip allows adding so called console scripts, which are shell commands that execute some function in you program. You can add console scripts in a section [project.scripts]. The keys are the script names while the values are the path to the function in the format some.module.path:class.function, where the class part is optional. The function is called with no arguments. Example:

[project.scripts]
get_42 = "my_project:DummyClass.get_42"

You can also specify trove classifiers in your Cargo.toml under project.classifiers:

[project]
name = "my-project"
classifiers = ["Programming Language :: Python"]

Source distribution

maturin supports building through pyproject.toml. To use it, create a pyproject.toml next to your Cargo.toml with the following content:

[build-system]
requires = ["maturin>=0.12,<0.13"]
build-backend = "maturin"

If a pyproject.toml with a [build-system] entry is present, maturin will build a source distribution of your package, unless --no-sdist is specified. The source distribution will contain the same files as cargo package. To only build a source distribution, pass --interpreter without any values.

You can then e.g. install your package with pip install .. With pip install . -v you can see the output of cargo and maturin.

You can use the options compatibility, skip-auditwheel, bindings, strip, cargo-extra-args and rustc-extra-args under [tool.maturin] the same way you would when running maturin directly. The bindings key is required for cffi and bin projects as those can't be automatically detected. Currently, all builds are in release mode (see this thread for details).

For a non-manylinux build with cffi bindings you could use the following:

[build-system]
requires = ["maturin>=0.12,<0.13"]
build-backend = "maturin"

[tool.maturin]
bindings = "cffi"
compatibility = "linux"

manylinux option is also accepted as an alias of compatibility for backward compatibility with old version of maturin.

To include arbitrary files in the sdist for use during compilation specify sdist-include as an array of globs:

[tool.maturin]
sdist-include = ["path/**/*"]

There's a maturin sdist command for only building a source distribution as workaround for pypa/pip#6041.

Manylinux and auditwheel

For portability reasons, native python modules on linux must only dynamically link a set of very few libraries which are installed basically everywhere, hence the name manylinux. The pypa offers special docker images and a tool called auditwheel to ensure compliance with the manylinux rules. If you want to publish widely usable wheels for linux pypi, you need to use a manylinux docker image.

The Rust compiler since version 1.47 requires at least glibc 2.11, so you need to use at least manylinux2010. For publishing, we recommend enforcing the same manylinux version as the image with the manylinux flag, e.g. use --manylinux 2014 if you are building in quay.io/pypa/manylinux2014_x86_64. The messense/maturin-action github action already takes care of this if you set e.g. manylinux: 2014.

maturin contains a reimplementation of auditwheel automatically checks the generated library and gives the wheel the proper. If your system's glibc is too new or you link other shared libraries, it will assign the linux tag. You can also manually disable those checks and directly use native linux target with --manylinux off.

For full manylinux compliance you need to compile in a CentOS docker container. The konstin2/maturin image is based on the manylinux2010 image, and passes arguments to the maturin binary. You can use it like this:

docker run --rm -v $(pwd):/io konstin2/maturin build --release  # or other maturin arguments

Note that this image is very basic and only contains python, maturin and stable rust. If you need additional tools, you can run commands inside the manylinux container. See konstin/complex-manylinux-maturin-docker for a small educational example or nanoporetech/fast-ctc-decode for a real world setup.

maturin itself is manylinux compliant when compiled for the musl target.

Code

The main part is the maturin library, which is completely documented and should be well integrable. The accompanying main.rs takes care username and password for the pypi upload and otherwise calls into the library.

The sysconfig folder contains the output of python -m sysconfig for different python versions and platform, which is helpful during development.

You need to install cffi and virtualenv (pip install cffi virtualenv) to run the tests.

There are some optional hacks that can speed up the tests (over 80s to 17s on my machine).

By running cargo build --release --manifest-path test-crates/cargo-mock/Cargo.toml you can activate a cargo cache avoiding to rebuild the pyo3 test crates with every python version.
Delete target/test-cache to clear the cache (e.g. after changing a test crate) or remove test-crates/cargo-mock/target/release/cargo to deactivate it.
By running the tests with the faster-tests feature, binaries are stripped and wheels are only stored and not compressed.

Contextualist/maturin