Development Status
- 5 - Production/Stable
Intended Audience
- Developers
Operating System
- OS Independent
Programming Language
- Python
- Python :: 3
- Python :: 3.8
- Python :: 3.9
- Python :: 3.10
- Python :: 3.11
- Python :: 3.12
- Python :: 3.13
- Python :: 3.14
- Python :: Implementation :: CPython
- Python :: Implementation :: PyPy
- Python :: Implementation :: Stackless
- C
- C++
- Cython
Topic
- Software Development :: Code Generators
- Software Development :: Compilers
- Software Development :: Libraries :: Python Modules
Typing
- Typed
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 with:
NO_CYTHON_COMPILE=true pip install .
3.2.9 (2026-07-23)
Bugs fixed
Indexing into freshly created lists with an out-of-bounds index could crash. (Github issue https://github.com/cython/cython/issues/7793)
Function arguments with default values could end up uninitialised in closures, leading to crashes. Patch by Anthony Donlon. (Github issue https://github.com/cython/cython/issues/7782)
bytearray.append(None) could crash. The optimised code was also lacking concurrency guards. (Github issue https://github.com/cython/cython/issues/7796)
Some rare corner cases when concatenating text strings were resolved. (Github issue https://github.com/cython/cython/issues/7799)
Assignments of builtin string types to typedefs of object could erroneously be rejected. (Github issue https://github.com/cython/cython/issues/7789)
Subscripting type failed with a TypeError. (Github issue https://github.com/cython/cython/issues/5563)
Manually disabling CYTHON_VECTORCALL in CPython could lead to invalid C code. Patch by Florent Gallaire. (Github issue https://github.com/cython/cython/issues/7807)
Some internal Limited API version checks for Py3.12 were corrected. (Github issue https://github.com/cython/cython/issues/7845)