Python Developer’s Guide

This guide is a comprehensive resource for contributing to Python – for both new and experienced contributors. It is maintained by the same community that maintains Python. We welcome your contributions!

Contributing

We encourage everyone to contribute to Python. To help you, we have put up this developer’s guide. If you still have questions after reviewing the material in this guide, then the Core Python Mentorship group is available to help guide new contributors through the process.

Guide for contributing to Python:

Documentation

Code

Triage

We recommend that sections of this guide be read as needed. You can stop where you feel comfortable and begin contributing immediately without reading and understanding everything. If you do choose to skip around within the guide, be aware that sections build on each other, so you may find it necessary to backtrack to fill in missing concepts and terminology.

A number of individuals from the Python community have contributed to a series of excellent guides at Open Source Guides.

Quick reference

Here are the basic steps needed to get set up and open a pull request. This is meant as a checklist, once you know the basics. For complete instructions please see the setup guide.

  1. Install and set up Git and other dependencies (see the Git Setup page for detailed information).

  2. Fork the CPython repository to your GitHub account and get the source code using:

    git clone https://github.com/<your_username>/cpython
cd cpython

  3. Build Python:

    ./configure --with-pydebug && make -j $(nproc)

    ./configure --with-pydebug && make -j8

    PCbuild\build.bat -e -d

    See also more detailed instructions, how to install and build dependencies, and the platform-specific pages for Unix, macOS, and Windows.

  4. Run the tests:

    ./python -m test -j3

    ./python.exe -m test -j8

    Note

    Most macOS systems use ./python.exe in order to avoid filename conflicts with the Python directory.

    .\python.bat -m test -j3

  5. Create a new branch where your work for the issue will go, for example:

    git checkout -b fix-issue-12345 main

    If an issue does not already exist, please create it. Trivial issues (for example, typos) do not require an issue.

  6. Once you fix the issue, run the tests and pre-commit:

    pre-commit install
pre-commit run --all-files

    See Install pre-commit as a Git hook for more details. If everything is ok, commit.

  7. Push the branch on your fork on GitHub and create a pull request. Include the issue number using gh-NNNNNN in the pull request title. For example:

    gh-12345: Fix some bug in spam module

  8. Add a News entry into the Misc/NEWS.d/ directory as individual file. The news entry can be created by using blurb-it, or the blurb tool and its blurb add command. Please read more about blurb in its repository.

Note

First time contributors will need to sign the Contributor Licensing Agreement (CLA) as described in the Licensing section of this guide.

Proposing changes to Python itself

Improving Python’s code, documentation and tests are ongoing tasks that are never going to be “finished”, as Python operates as part of an ever-evolving system of technology. An even more challenging ongoing task than these necessary maintenance activities is finding ways to make Python, in the form of the standard library and the language definition, an even better tool in a developer’s toolkit.

While these kinds of change are much rarer than those described above, they do happen and that process is also described as part of this guide:

Key resources

Additional resources

Code of conduct

Please note that all interactions on Python Software Foundation-supported infrastructure is covered by the PSF Code of Conduct, which includes all infrastructure used in the development of Python itself (for example, Discourse, issue trackers, GitHub, and so on). In general this means everyone is expected to be open, considerate, and respectful of others no matter what their position is within the project.

Other interpreter implementations

This guide is specifically for contributing to the Python reference interpreter, also known as CPython (while most of the standard library is written in Python, the interpreter core is written in C and integrates most easily with the C and C++ ecosystems).

There are other Python implementations, each with a different focus. Like CPython, they always have more things they would like to do than they have developers to work on them. Some major examples that may be of interest are:

  • PyPy: A Python interpreter focused on high speed (JIT-compiled) operation on major platforms.

  • GraalPy: A Python interpreter which has first-class support for embedding in Java, built on GraalVM.

  • Jython: A Python interpreter focused on good integration with the Java Virtual Machine (JVM) environment.

  • IronPython: A Python interpreter focused on good integration with the Common Language Runtime (CLR) provided by .NET and Mono.

  • MicroPython: A tiny Python interpreter with small subset of the Python standard library that is optimised to run on microcontrollers and in constrained environments.

  • CircuitPython: A fork of MicroPython designed to simplify experimenting and learning to code on low-cost microcontroller boards.

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