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.

Usage

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

pip install maturin

There are three main commands:

• 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.
• 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.

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.

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. Aternatively 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.

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
├── 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

To specify python dependencies, add a list requires-dist in a [package.metadata.maturin] section in the Cargo.toml. This list is equivalent to install_requires in setuptools:

[package.metadata.maturin]
requires-dist = ["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 [package.metadata.maturin.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:

[package.metadata.maturin.scripts]
get_42 = "my_project:DummyClass.get_42"

You can also specify trove classifiers in your Cargo.toml under package.metadata.maturin.classifiers:

[package.metadata.maturin]
classifiers = ["Programming Language :: Python"]

Note that package.metadata.maturin.classifier is also supported for backwards compatibility.

You can use other fields from the python core metadata in the [package.metadata.maturin] section, specifically maintainer, maintainer-email and requires-python (string fields), as well as requires-external and provides-extra (lists of strings) and project-url (dictionary string to string)

pyproject.toml

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>=0.10,<0.11"]
build-backend = "maturin"

If a pyproject.toml with a [build-system] entry is present, maturin will build a source distribution (sdist) 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 manylinux, 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>=0.10,<0.11"]
build-backend = "maturin"

[tool.maturin]
bindings = "cffi"
manylinux = "off"

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 cargo 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.

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 6 docker container. The konstin2/maturin image is based on the official manylinux image. You can use it like this:

docker run --rm -v $(pwd):/io konstin2/maturin build

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. The binaries on the release pages have additional keyring integration (through the password-storage feature), which is not manylinux compliant.

PyPy

maturin can build and upload wheels for pypy with pyo3. This pypy has been only tested manually with pypy3.7-7.3 and on linux. See #115 for more details.

Build

USAGE:
    maturin build [FLAGS] [OPTIONS]

FLAGS:
    -h, --help
            Prints help information

        --no-sdist
            Don't build a source distribution

        --release
            Pass --release to cargo

        --skip-auditwheel
            Don't check for manylinux compliance

        --strip
            Strip the library for minimum file size

        --universal2
            Control whether to build universal2 wheel for macOS or not. Only applies to macOS targets, do nothing
            otherwise
    -V, --version
            Prints version information


OPTIONS:
    -m, --manifest-path <PATH>
            The path to the Cargo.toml [default: Cargo.toml]

        --target <TRIPLE>
            The --target option for cargo [env: CARGO_BUILD_TARGET=]

    -b, --bindings <bindings>
            Which kind of bindings to use. Possible values are pyo3, rust-cpython, cffi and bin

        --cargo-extra-args <cargo-extra-args>...
            Extra arguments that will be passed to cargo as `cargo rustc [...] [arg1] [arg2] -- [...]`

            Use as `--cargo-extra-args="--my-arg"`

            Note that maturin invokes cargo twice: Once as `cargo metadata` and then as `cargo rustc`. maturin tries to
            pass only the shared subset of options to cargo metadata, but this is may be a bit flaky.
    -i, --interpreter <interpreter>...
            The python versions to build wheels for, given as the names of the interpreters. Uses autodiscovery if not
            explicitly set
        --manylinux <manylinux>
            Control the platform tag on linux. Options are `2010` (for manylinux2010), `2014` (for manylinux2014),
            `2_24` (for manylinux_2_24) and `off` (for the native linux tag). Note that manylinux1 is unsupported by the
            rust compiler. Wheels with the native `linux` tag will be rejected by pypi, unless they are separately
            validated by `auditwheel`.

            The default is the lowest compatible, of plain `linux` if nothing matched

            This option is ignored on all non-linux platforms [possible values: 2010, 2014, 2_24, off]
    -o, --out <out>
            The directory to store the built wheels in. Defaults to a new "wheels" directory in the project's target
            directory
        --rustc-extra-args <rustc-extra-args>...
            Extra arguments that will be passed to rustc as `cargo rustc [...] -- [...] [arg1] [arg2]`

            Use as `--rustc-extra-args="--my-arg"`

Publish

USAGE:
    maturin publish [FLAGS] [OPTIONS]

FLAGS:
        --debug
            Do not pass --release to cargo

    -h, --help
            Prints help information

        --no-sdist
            Don't build a source distribution

        --no-strip
            Do not strip the library for minimum file size

        --skip-auditwheel
            Don't check for manylinux compliance

        --skip-existing
            Continue uploading files if one already exists. (Only valid when uploading to PyPI. Other implementations
            may not support this.)
        --universal2
            Control whether to build universal2 wheel for macOS or not. Only applies to macOS targets, do nothing
            otherwise
    -V, --version
            Prints version information


OPTIONS:
    -m, --manifest-path <PATH>
            The path to the Cargo.toml [default: Cargo.toml]

        --target <TRIPLE>
            The --target option for cargo [env: CARGO_BUILD_TARGET=]

    -b, --bindings <bindings>
            Which kind of bindings to use. Possible values are pyo3, rust-cpython, cffi and bin

        --cargo-extra-args <cargo-extra-args>...
            Extra arguments that will be passed to cargo as `cargo rustc [...] [arg1] [arg2] -- [...]`

            Use as `--cargo-extra-args="--my-arg"`

            Note that maturin invokes cargo twice: Once as `cargo metadata` and then as `cargo rustc`. maturin tries to
            pass only the shared subset of options to cargo metadata, but this is may be a bit flaky.
    -i, --interpreter <interpreter>...
            The python versions to build wheels for, given as the names of the interpreters. Uses autodiscovery if not
            explicitly set
        --manylinux <manylinux>
            Control the platform tag on linux. Options are `2010` (for manylinux2010), `2014` (for manylinux2014),
            `2_24` (for manylinux_2_24) and `off` (for the native linux tag). Note that manylinux1 is unsupported by the
            rust compiler. Wheels with the native `linux` tag will be rejected by pypi, unless they are separately
            validated by `auditwheel`.

            The default is the lowest compatible, of plain `linux` if nothing matched

            This option is ignored on all non-linux platforms [possible values: 2010, 2014, 2_24, off]
    -o, --out <out>
            The directory to store the built wheels in. Defaults to a new "wheels" directory in the project's target
            directory
    -p, --password <password>
            Password for pypi or your custom registry. Note that you can also pass the password through MATURIN_PASSWORD

    -r, --repository-url <registry>
            The url of registry where the wheels are uploaded to [default: https://upload.pypi.org/legacy/]

        --rustc-extra-args <rustc-extra-args>...
            Extra arguments that will be passed to rustc as `cargo rustc [...] -- [...] [arg1] [arg2]`

            Use as `--rustc-extra-args="--my-arg"`
    -u, --username <username>
            Username for pypi or your custom registry

Develop

USAGE:
    maturin develop [FLAGS] [OPTIONS]

FLAGS:
    -h, --help
            Prints help information

        --release
            Pass --release to cargo

        --strip
            Strip the library for minimum file size

    -V, --version
            Prints version information


OPTIONS:
    -b, --binding-crate <binding-crate>
            Which kind of bindings to use. Possible values are pyo3, rust-cpython, cffi and bin

        --cargo-extra-args <cargo-extra-args>...
            Extra arguments that will be passed to cargo as `cargo rustc [...] [arg1] [arg2] --`

            Use as `--cargo-extra-args="--my-arg"`
    -m, --manifest-path <manifest-path>
            The path to the Cargo.toml [default: Cargo.toml]

        --rustc-extra-args <rustc-extra-args>...
            Extra arguments that will be passed to rustc as `cargo rustc [...] -- [arg1] [arg2]`

            Use as `--rustc-extra-args="--my-arg"`

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 two 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.

You might want to have look into my by now slightly outdated blog post which explains the intricacies of building native python packages.