Build CPython 3.13 by default - #1950

I see some CI failing. I think one error is the free_threaded 3.13 now being expected to build, but doesn't, so I need to update that test.

The other errors I don't understand directly, so some help with them is appreciated!

Maintainers, feel free to directly modify this PR (push to this branch) by the way.

Ah I missed that one, thanks! So far it all looks green.

There we go, all green!

Thanks for merging!

In what timeframe do you think a new release would be possible?

If it depends on me, tonight.

I found that on macOS and Windows it is still necessary to add CIBW_PRERELEASE_PYTHONS: True. Just thought I'd ask here - was that intended?

No, it shouldn’t be

Boost-histogram is building 3.13 windows wheels (and macOS both flavors) without the flag, just checked. Is this 3.13 in general or maybe 3.13t? We will be releasing a new patch release of pybind11 with PyMutex, then I’ll be trying that (3.13t) in boost-histogram.

Pyinstrument is building 3.13 without the flag, too.

Okay, never mind then, it's probably something else (even if adding the env var fixed it for me). And it was regular cp313. For the record:

• failing run
• passing run
• commit that made the difference

You'll need v2.20.0 , you're on 2.19.0 :)

(Or, at least you were in the failing run)

(2.20 is also the one with the ABI stable Python 3.13rc1)

Argh, made the updates to 2.20 but missed one indeed, for Windows. And the macOS ones were free-threaded. Sorry for the noise.

Now that everyone had about 3 months to get their Python 3.13 wheels building, and 3.13 was released as stable, would this be a good time to talk about building Python 3.13 free-threaded (cp313t) wheels by default?

Just my two cents but I don't think free-threading wheels should be built by default as long as the feature is considered experimental by CPython developers.

One thing that might have improved the experience would be if we could detect and enable automatically if the free-threaded classifiers were present. However, the free-threaded classifiers discussion devolved into bike-shedding and died. pypa/trove-classifiers#177 & https://discuss.python.org/t/free-threading-trove-classifier/62406