How to Install `Cython` in Python

v3.2.4 General Purpose Python >=3.8 Apache-2.0

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

Install pip install Cython

What is Cython?

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

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.

Documentation → PyPI page → Author: Robert Bradshaw, Stefan Behnel, David Woods, Greg Ewing, et al.

Quick Start

Minimal example to get started with Cython:

import cython

print(cython.__version__)

Installation

pip (standard)

pip install Cython

Virtual environment (recommended)

python -m venv venv
source venv/bin/activate   # Windows: venv\Scripts\activate
pip install Cython

pip3

pip3 install Cython

conda

conda install -c conda-forge Cython

Poetry

poetry add Cython

Verify the Installation

After installing, confirm the package is available:

python -c "import cython; print(cython.__version__)"

If this prints a version number, installation succeeded. If you see a ModuleNotFoundError, see the errors section below.

Installation Errors

Common errors when installing Cython with pip.

ModuleNotFoundError: No module named 'cython'

Cause: The package is not installed in the current Python environment.

Fix: Run pip install Cython. If using a virtual environment, ensure it is activated first.

ModuleNotFoundError: No module named 'cython' (installed but still failing)

Cause: pip installed the package into a different Python than the one running your script.

Fix: Use python -m pip install Cython to install into the interpreter you are running.

ImportError: cannot import name 'X' from 'cython'

Cause: The function or class does not exist in the installed version.

Fix: Check the version with pip show Cython and upgrade with pip install --upgrade Cython.

pip: command not found

Cause: pip is not in PATH or Python was not added to PATH during installation.

Fix: Try python -m pip install Cython. On macOS/Linux try pip3.

PermissionError: [Errno 13] Permission denied

Cause: No write access to the system Python package directory.

Fix: Use a virtual environment, or add --user: pip install --user Cython

SSL: CERTIFICATE_VERIFY_FAILED

Cause: pip cannot verify PyPI's SSL certificate — common behind corporate proxies.

Fix: Try: pip install --trusted-host pypi.org --trusted-host files.pythonhosted.org Cython

Recent Releases

Version	Released
`3.2.4` latest	2026-01-04
`3.1.8`	2026-01-03
`3.2.3`	2025-12-14
`3.2.2`	2025-11-30
`3.1.7`	2025-11-12

Full release history on PyPI →

Manage Cython

Upgrade to latest version

pip install --upgrade Cython

Install a specific version

pip install Cython==3.2.4

Uninstall

pip uninstall Cython

Check what is installed

pip show Cython

Last updated: 2026-04-11 • Data from PyPI

How to Install Cython in Python