ENH: Python 3.13 free-threading support

[lysnikolaou]

This aims to be a tracking issue for all work necessary to support the free-threaded build of Python 3.13. A very high-level list of steps is (more details to follow as I investigate more issues):

• Set up CI for free-threading
  • CI: Set up CI for the free-threaded build of 3.13 #59058
• Audit C extension module for thread-safety issues
  • pandas_datetime is thread-safe
  • pandas_parser is not thread-safe, but cannot be used in multiple threads from within pandas Python code.
• Test Cython extension modules (with Freethreading thread safety cython/cython#6226)
  • Everything appears to be okay (green CI) both with Cython nightly and with the above Cython PR!
• Mark C extension modules as thread-safe with the Py_mod_gil slot
  • Add Py_mod_gil slot to C extension modules #59135
  • ENH: Globally enable Cython free-threading directive #59248
• Upload nightly wheels for the free-threaded build
  • Upload 3.13 & free-threaded nightly wheels #59136

[xbit18]

Hi! I'm currently writing a thesis on free-threading python and wonder if there's any estimate on how much time this would take

[lysnikolaou]

Hello! An initial investigation shows that it should be relatively straight-forward to get a passing test suite under the free-threaded build. However, if you're looking for a full release with support for it, it's still probably going to be a few weeks/months, since Python 3.13 is not final (not even in rc) yet.

Maybe a maintainer could answer this better than me as well.

[xbit18]

Yeah I'm only in need of a "preliminary" implementation to run some really simple tests involving a dataframe with python 3.13.0b2 with the free threading build. Right now it's not even installing correctly.

[lesteve]

Yeah I'm only in need of a "preliminary" implementation to run some really simple tests involving a dataframe with python 3.13.0b2 with the free threading build. Right now it's not even installing correctly.

@xbit18 you probably have managed to do it since your last comment but the https://py-free-threading.github.io doc has a lot of useful info in particular:

• how to install a free-threaded CPython: https://py-free-threading.github.io/installing_cpython/
• how to install packages and which packages already provide development wheels compatible with CPython 3.13 free-threaded: https://py-free-threading.github.io/tracking/

[lysnikolaou]

I'm trying to get Windows wheels to build successfully as well. It seems like it's an easy task to build them, but not as easy to test them, because Windows wheels are tested on windowsservercore instead of the GHA runner.

@mroeschke You implemented this in #53087. Is there any way around it? There's this comment in the workflow file. Could you elaborate on it?

# Testing on windowsservercore instead of GHA runner to fail on missing DLLs

The Docker images do not contain a free-threaded build, so it's currently impossible to do this for the free-threaded wheels. Should we enable cibuildwheel tests and disable the Docker ones for free-threaded Windows wheels maybe? Would that be okay?

[mroeschke]

Maybe it's not entirely necessary to test these wheels on a separate Docker image anymore and just use the windows images from the GHA runner if that makes this easier

[ngoldbaum]

FWIW @lesteve just let me know over in a scikit-learn issue that scikit-learn is going to need the docker images as well.

[Alec1198055421]

hi， How long until Python 3.13's free-threading support is complete?