This tracking issue aims to collect all the issues and PRs related for the upcoming free-threaded CPython 3.13 (a.k.a. "no-GIL") builds. Until now, as of #28610 all the test suite is passing (at least locally).

Right now, a complete triaging of all modules is required in order to detect any potential concurrency issues (C-thread safety issues), in order to either fix them or mark them as non-free-threaded compliant.

We invite the community and maintainers with extensive knowledge of the project to highlight the existence of any potential thread-safety issues that currently exist.

Here are some resources that might be useful in the context of free-threaded Python

• PEP 703
• Corresponding tracker in NumPy: ENH: Support free-threaded python build (tracking issue) numpy/numpy#26157
• Corresponding tracker in SciPy: Tracker: Support free-threaded CPython builds scipy/scipy#20669
• Corresponding tracker in Pillow: Python 3.13 free-threading compatibility python-pillow/Pillow#8199
• Corresponding tracker in Pandas: ENH: Python 3.13 free-threading support pandas-dev/pandas#59057
• Corresponding tracker in Scikit-image: Tracker: free-threaded Python support scikit-image/scikit-image#7464
• Free-threaded Python community Wiki: https://py-free-threading.github.io/

Pull Requests

• CI: Add CI to test matplotlib against free-threaded Python #28610