ENH: Support for Python 3.13.2 free-threading version

[qfcy]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

Firstly, use python3.13t -m pip install pandas to build and install pandas on VS 16.11.43 and MSVC 19.29.30158.
Then try to import it:

E:\Git-repositories\project179>python3.13t
Python 3.13.2 experimental free-threading build (tags/v3.13.2:4f8bb39, Feb  4 2025, 15:33:40) [MSC v.1942 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import pandas as pd
<Segmentation fault caused there>

Issue Description

The line import pandas failed in Python 3.13 free-threading version on x64 Windows.
As I tried to execute it, a segmentation fault caused because I've seen werfault.exe appeared in the task manager.

Expected Behavior

The line import pandas successfully be executed.

Installed Versions

pandas 2.2.3 (Note: cannot call pd.show_versions() as I couldn't import pandas at the first step)

Additionally, this is the output during compiling pandas that contains the MSVC version:

 + meson setup C:\Users\admin\AppData\Local\Temp\pip-install-yk54bvta\pandas_93cffcf8ab364c6d8ccc39766c5b148a C:\Users\admin\AppData\Local\Temp\pip-install-yk54bvta\pandas_93cffcf8ab364c6d8ccc39766c5b148a\.mesonpy-6btzqpgz\build -Dbuildtype=release -Db_ndebug=if-release -Db_vscrt=md --vsenv --native-file=C:\Users\admin\AppData\Local\Temp\pip-install-yk54bvta\pandas_93cffcf8ab364c6d8ccc39766c5b148a\.mesonpy-6btzqpgz\build\meson-python-native-file.ini
      The Meson build system
      Version: 1.2.1
      Source dir: C:\Users\admin\AppData\Local\Temp\pip-install-yk54bvta\pandas_93cffcf8ab364c6d8ccc39766c5b148a
      Build dir: C:\Users\admin\AppData\Local\Temp\pip-install-yk54bvta\pandas_93cffcf8ab364c6d8ccc39766c5b148a\.mesonpy-6btzqpgz\build
      Build type: native build
      Project name: pandas
      Project version: 2.2.3
      Activating VS 16.11.43
      C compiler for the host machine: cl (msvc 19.29.30158 "用于 x64 的 Microsoft (R) C/C++ 优化编译器 19.29.30158 版")
      C linker for the host machine: link link 14.29.30158.0
      C++ compiler for the host machine: cl (msvc 19.29.30158 "用于 x64 的 Microsoft (R) C/C++ 优化编译器 19.29.30158 版")
      C++ linker for the host machine: link link 14.29.30158.0
      Cython compiler for the host machine: cython (cython 3.0.12)
      Host machine cpu family: x86_64
      Host machine cpu: x86_64
      Program python found: YES (D:\Python\Python313\python3.13t.exe)
      Run-time dependency python found: YES 3.13
      Build targets in project: 53

      pandas 2.2.3

        User defined options
          Native files: C:\Users\admin\AppData\Local\Temp\pip-install-yk54bvta\pandas_93cffcf8ab364c6d8ccc39766c5b148a\.mesonpy-6btzqpgz\build\meson-python-native-file.ini
          buildtype   : release
          vsenv       : True
          b_ndebug    : if-release
          b_vscrt     : md

      Found ninja.EXE-1.11.1.git.kitware.jobserver-1 at C:\Users\admin\AppData\Local\Temp\pip-build-env-3jrexmoi\normal\Scripts\ninja.EXE

      Visual Studio environment is needed to run Ninja. It is recommended to use Meson wrapper:
      C:\Users\admin\AppData\Local\Temp\pip-build-env-3jrexmoi\overlay\Scripts\meson compile -C .
      + meson compile
      [1/151] Generating pandas/_libs/algos_common_helper_pxi with a custom command
      [2/151] Generating pandas/_libs/khash_primitive_helper_pxi with a custom command
      [3/151] Generating pandas/_libs/hashtable_class_helper_pxi with a custom command
      [4/151] Generating pandas/_libs/algos_take_helper_pxi with a custom command
      [5/151] Generating pandas/_libs/hashtable_func_helper_pxi with a custom command
      [6/151] Generating pandas/_libs/intervaltree_helper_pxi with a custom command
      [7/151] Generating pandas/_libs/index_class_helper_pxi with a custom command
      [8/151] Generating pandas/_libs/sparse_op_helper_pxi with a custom command
      [9/151] Generating pandas/__init__.py with a custom command
      [10/151] Compiling C object pandas/_libs/tslibs/parsing.cp313t-win_amd64.pyd.p/.._src_parser_tokenizer.c.obj
      ..\..\pandas\_libs\include\pandas/vendored/klib/khash.h(729): warning C4090: “函数”: 不同的“const”限定符
      [11/151] Compiling Cython source C:/Users/admin/AppData/Local/Temp/pip-install-yk54bvta/pandas_93cffcf8ab364c6d8ccc39766c5b148a/pandas/_libs/tslibs/base.pyx
      [12/151] Compiling C object pandas/_libs/tslibs/base.cp313t-win_amd64.pyd.p/meson-generated_pandas__libs_tslibs_base.pyx.c.obj

[rhshadrach]

Thanks for the report. Cython is still working on support (but it seems 3.1 is getting close). pandas cannot support free-threading until after Cython is ready. Even then, it's not clear to me what the level of effort it will take to support free-threading. Work on this is certainly appreciated!

Reworking this issue as an enhancement.

[rgommers]

Cython 3.1.0 is available, so this should now work fine. Also, nightly Windows wheels for free-threaded CPython are available at https://anaconda.org/scientific-python-nightly-wheels/pandas, so there's no longer a need to build from source. They pass all tests, so I think this issue can be closed.

[rhshadrach]

Thanks @rgommers - I plan to close this issue after updating our dev environment to use Cython 3.1. Want to run the full ASV suite first.

[rgommers]

Sounds good, thanks @rhshadrach

[qfcy]

Now pandas can be certainly built successfully, but the segmentation fault hasn't been fixed:

C:\Users\admin>py313t -m pip install pandas
Looking in indexes: https://pypi.tuna.tsinghua.edu.cn/simple/
Collecting pandas
  Downloading https://pypi.tuna.tsinghua.edu.cn/packages/9c/d6/9f8431bacc2e19dca897724cd097b1bb224a6ad5433784a44b587c7c13af/pandas-2.2.3.tar.gz (4.4 MB)
     ---------------------------------------- 4.4/4.4 MB 36.0 MB/s eta 0:00:00
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
  Installing backend dependencies ... done
  Preparing metadata (pyproject.toml) ... done
Requirement already satisfied: numpy>=1.26.0 in d:\python\python313\lib\site-packages (from pandas) (2.2.6)
Requirement already satisfied: python-dateutil>=2.8.2 in d:\python\python313\lib\site-packages (from pandas) (2.9.0.post0)
Requirement already satisfied: pytz>=2020.1 in d:\python\python313\lib\site-packages (from pandas) (2025.1)
Requirement already satisfied: tzdata>=2022.7 in d:\python\python313\lib\site-packages (from pandas) (2025.1)
Requirement already satisfied: six>=1.5 in d:\python\python313\lib\site-packages (from python-dateutil>=2.8.2->pandas) (1.17.0)
Building wheels for collected packages: pandas
  Building wheel for pandas (pyproject.toml) ... done
  Created wheel for pandas: filename=pandas-2.2.3-cp313-cp313t-win_amd64.whl size=39033716 sha256=b99517674c7dfaae923c9682bd970bb9db0c7cce192423355e394879c7347837
  Stored in directory: c:\users\admin\appdata\local\pip\cache\wheels\b3\3a\9c\4853eb9b64bf66e233d1ec029b2098492524487e3ba8370e28
Successfully built pandas
Installing collected packages: pandas
Successfully installed pandas-2.2.3

The same segmentation fault:

C:\Users\admin>py313t
Python 3.13.3 experimental free-threading build (tags/v3.13.3:6280bb5, Apr  8 2025, 14:53:12) [MSC v.1943 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import pandas as pd
<Segmentation fault caused there>