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 to Python!

Quick Reference

Here are the basic steps needed to get set up and contribute a patch. 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 Get Setup page for detailed information).

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

    git clone<your_username>/cpython
  3. Build Python, on UNIX and Mac OS use:

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

    and on Windows use:

    PCbuild\build.bat -e -d

    See also more detailed instructions, how to build dependencies, and the plaform-specific pages for UNIX, Mac OS, and Windows.

  4. Run the tests:

    ./python -m test -j3

    On most Mac OS X systems, replace ./python with ./python.exe. On Windows, use python.bat. With Python 2.7, replace test with test.regrtest.

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

    git checkout -b fix-issue-12345 master

    If an issue does not already exist, please create it. Trivial issues (e.g. typo fixes) do not require any issue to be created.

  6. Once you fixed the issue, run the tests, run make patchcheck, and if everything is ok, commit.

  7. Push the branch on your fork on GitHub and create a pull request. Include the issue number using bpo-NNNN in the pull request description. For example:

    bpo-12345: Fix some bug in spam module


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

Status of Python branches

Branch Schedule Status First release End-of-life Comment
master PEP 569 features 2019-10-20 2024-10 The master branch is currently the future Python 3.8.
3.7 PEP 537 bugfix 2018-06-27 2023-06-27 Most recent binary release: Python 3.7.0
3.6 PEP 494 bugfix 2016-12-23 2021-12-23 Most recent binary release: Python 3.6.6
2.7 PEP 373 bugfix 2010-07-03 2020-01-01 The support has been extended to 2020-01-01. Most recent binary release: Python 2.7.15
3.5 PEP 478 security 2015-09-13 2020-09-13 Most recent security release: Python 3.5.5
3.4 PEP 429 security 2014-03-16 2019-03-16 Most recent security release: Python 3.4.8


features:new features are only added to the master branch, this branch accepts any kind of change.
prerelease:feature fixes, bugfixes and security fixes are accepted for the upcoming feature release.
bugfix:bugfixes and security fixes are accepted, new binaries are still released.
security:only security fixes are accepted and no more binaries are released, but new source-only versions can be released
end-of-life:release cycle is frozen; no further changes can be pushed to it.

Dates in italic are scheduled and can be adjusted.

By default, the end-of-life is scheduled 5 years after the first release. It can be adjusted by the release manager of each branch. Versions older than 2.7 have reached end-of-life.

See also Security branches.

Each release of Python is tagged in the source repo with a tag of the form vX.Y.ZTN, where X is the major version, Y is the minor version, Z is the micro version, T is the release level (a for alpha releases, b for beta, rc release candidate, and null for final releases), and N is the release serial number. Some examples of release tags: v3.7.0a1, v3.6.3, v2.7.14rc1.

The code base for a release cycle which has reached end-of-life status is frozen and no longer has a branch in the repo. The final state of the end-of-lifed branch is recorded as a tag with the same name as the former branch, e.g. 3.3 or 2.6. For reference, here are the most recently end-of-lifed release cycles:

Tag Schedule Status First release End-of-life Comment
3.3 PEP 398 end-of-life 2012-09-29 2017-09-29 Final release: Python 3.3.7
3.2 PEP 392 end-of-life 2011-02-20 2016-02-20 Final release: Python 3.2.6
3.1 PEP 375 end-of-life 2009-06-27 2012-04-09 Final release: Python 3.1.5
3.0 PEP 361 end-of-life 2008-12-03 2009-01-13 Final release: Python 3.0.1
2.6 PEP 361 end-of-life 2008-10-01 2013-10-29 Final release: Python 2.6.9


We encourage everyone to contribute to Python and that’s why 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.

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

Core developers and contributors alike will find the following guides useful:

Guide for contributing to Python:

New Contributors Documentarians Triagers Core Developers
Getting Started Helping with Documentation Issue Tracking How to Become a Core Developer
Where to Get Help Documenting Python Triaging an Issue Developer Log
Lifecycle of a Pull Request Style guide Helping Triage Issues Accepting Pull Requests
Running & Writing Tests reStructuredText Primer Experts Index Development Cycle
Fixing “easy” Issues (and Beyond)     Core Developer Motivations and Affiliations
Following Python’s Development     Core Developers Office Hours
Git Bootcamp and Cheat Sheet      

Advanced tasks and topics for once you are comfortable:

It is recommended that the above documents be read as needed. New contributors will build understanding of the CPython workflow by reading the sections mentioned in this table. You can stop where you feel comfortable and begin contributing immediately without reading and understanding these documents all at once. If you do choose to skip around within the documentation, be aware that it is written assuming preceding documentation has been read so you may find it necessary to backtrack to fill in missing concepts and terminology.

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:

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 example that may be of interest are:

  • PyPy: A Python interpreter focused on high speed (JIT-compiled) operation on major platforms
  • 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
  • Stackless: A Python interpreter focused on providing lightweight microthreads while remaining largely compatible with CPython specific extension modules

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 (e.g. mailing lists, issue trackers, GitHub, etc.). In general this means everyone is expected to be open, considerate, and respectful of others no matter what their position is within the project.

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