Python 3 is the default nowadays

[DimitriPapadopoulos]

No need to explicitly require Python 3.

[woodruffw]

I might be misunderstanding your PR's intent here, but this option doesn't have to do with Python 3 being the default or not: the reason we set 3.x is because setup-python strongly encourages the user to set some version; without an explicit version the runner's system Python is used, and that can be unpredictable/unreliable across runner changes.

TL;DR: This setting doesn't have anything to do with Python 2 vs. 3; it's here to make GitHub's CI/CD runners behave consistently. Removing this setting would expose us to default behavior that would be difficult to debug/diagnose since it only happens remotely.

[woodruffw]

Closing per above.

[DimitriPapadopoulos]

@woodruffw Precisely, 3.x is not "some version". I've read the setup-python documentation and haven't found anything to support the need for 3.x:
https://github.com/actions/setup-python/blob/main/docs/advanced-usage.md#using-the-python-version-input

Am I missing information that is absent from the setup-python documentation?

[woodruffw]

From the setup-python README:

The python-version input is optional. If not supplied, the action will try to resolve the version from the default .python-version file. If the .python-version file doesn't exist Python or PyPy version from the PATH will be used. The default version of Python or PyPy in PATH varies between runners and can be changed unexpectedly so we recommend always setting Python version explicitly using the python-version or python-version-file inputs.

twine doesn't provide a .python-version file, so the fallback behavior applies. In practice that means 3.8 or 3.9 (both EOL) on most runners. Either way, setting 3.x means that we get the latest stable Python 3.x release, which is what we want for the release workflow.

[DimitriPapadopoulos]

I see, thank you. The documentation is not clear enough about 3.x pulling the latest release of Python 3. I'll try to suggest an improvement.

[woodruffw]

The documentation is not clear enough about 3.x pulling the latest release of Python 3

I agree it could be clearer, although it is mentioned under "x-ranges" in the docs you linked.

(More generally, IMO it's an anti-feature that setup-python uses the system Python at all. But that's unfortunately probably pretty baked into their assumptions, I would guess.)