CPython

CPython is the reference implementation of the Python programming language, written in C and Python. This repository hosts the source code, standard library, build system, tests, and documentation for upcoming and current Python releases. The current development branch targets Python 3.15.

What is in this repository

The tree at https://github.com/python/cpython contains four kinds of code:

• The C interpreter and runtime under Python/, Objects/, Parser/, Modules/, Include/, and Programs/ — this builds the python3 executable.
• The standard library under Lib/ — the os, asyncio, typing, unittest, email, pathlib, pickle, ... pure-Python modules and packages that ship with every Python install.
• The test suite under Lib/test/ and Modules/_testcapi* — used by make test / python -m test.
• The build system, tooling and documentation — configure.ac, Makefile.pre.in, Tools/, Doc/, InternalDocs/, and the platform-specific directories PC/, PCbuild/, Mac/.

The current version is defined in Include/patchlevel.h (PY_MAJOR_VERSION / PY_MINOR_VERSION). The release schedule for 3.15 is described in PEP 790.

Where to look first

If you want to	Start here
Build CPython locally	Getting started
Understand the high-level design	Architecture
Read internal terminology	Glossary
Submit a patch	How to contribute
Trace source → bytes → execution	Compiler, Interpreter
Understand object layout and the type system	Object model
Understand how memory is managed	Memory allocator, GC
Understand the JIT (tier 2)	JIT and tier 2
Add or modify a stdlib module	Standard library
Write a C extension module that ships with core	C extension modules

Project links

• Website: https://www.python.org/
• Documentation: https://docs.python.org/
• Developer's guide: https://devguide.python.org/
• Issue tracker: https://github.com/python/cpython/issues
• Release schedule (3.15): PEP 790

License

CPython is distributed under the PSF License (a permissive, GPL-compatible license maintained by the Python Software Foundation). The repository contains no GPL code.