---
id: cython
version: "3.2.9"
license: Apache-2.0
license_treatment: permissive
maintenance: active
---

# Cython — The Cython compiler for writing C extensions in the Python language.

License: permissive · Maintenance: active · Popularity: top 1,000 on PyPI

## Install

pip install cython
uv add cython
poetry add cython

## Description

The Cython language makes writing C extensions for the Python language as
easy as Python itself.  Cython is a source code translator based on Pyrex_,
but supports more cutting edge functionality and optimizations.

The Cython language is a superset of the Python language (almost all Python
code is also valid Cython code), but Cython additionally supports optional
static typing to natively call C functions, operate with C++ classes and
declare fast C types on variables and class attributes.  This allows the
compiler to generate very efficient C code from Cython code.

This makes Cython the ideal language for writing glue code for external
C/C++ libraries, and for fast C modules that speed up the execution of
Python code.

The newest Cython release can always be downloaded from https://cython.org/.
Unpack the tarball or zip file, enter the directory, and then run::

    pip install .

Note that for one-time builds, e.g. for CI/testing, on platforms that are not
covered by one of the wheel packages provided on PyPI *and* the pure Python wheel
that we provide is not used, it is substantially faster than a full source build
to install an uncompiled (slower) version of Cython...

## AI interpretation — verify before relying

Cython is a source-to-source compiler that translates Python code with optional static type annotations into C, enabling you to write fast C extensions and glue code for C/C++ libraries while keeping Python syntax.

Verdict: Cython 3.2.9 is a stable, actively maintained compiler for writing performant C extensions in Python syntax. Zero known vulnerabilities, permissive licensing, and no runtime dependencies make it a low-risk choice. Recent bug fixes address edge cases in list indexing, closures, and string concatenation. Suitable for production use where C-level performance or C/C++ interop is needed.

[View on SkillFed](https://skillfed.io/packages/cython) · [View on PyPI](https://pypi.org/project/cython/)