The CPython Developer's Guide
This guide covers how to contribute to CPython. It is known by the nickname of "the devguide" by the Python core developers.
The official home of this guide is https://docs.python.org/devguide/, but an up-to-date mirror of this repository is also available at https://cpython-devguide.readthedocs.io/ (use the mirror if you want to verify that a recent change worked well as the copy on docs.python.org is updated only a few times a day).