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Comment by awinter-py | Hacker News Reader

wait then how does bdist_wheel know to make platform-dependent vs platform-independent whl files?

Your hunch is right, setuptools is able to determine if it's pure python or not (https://packaging.python.org/guides/distributing-packages-us...)

Maybe it's not reliable enough?

In any case, I can see why PyPI wouldn't want to increase the scope of their work. Sometimes is super valuable to just be good at one thing (distribute what others give you).

I think the pypi folks just don't have the resources / capacity to implement this. With appropriate funding this could have been done (development efforts wouldn't be that big, but probably operational costs for the build farms). In the past I ran (devpi builder)[https://github.com/blue-yonder/devpi-builder/] with (devpi)[https://pypi.org/project/devpi/] to build wheels for all my dependencies and keep them stored in a place I have control over.

That's a specific implementation that relies on setuptools. An sdist doesn't have to use setuptools to be an sdist.

Wheels can be generated out of thin air, there is no requirement that setuptools or any tool is ever involved, if you wanted you could zip up a particular directory structure and it is a wheel.

are you saying pure-python detection is possible for standard packaging formats like setuptools and pyproject.toml, but not for sdist generally?

pyproject.toml specifies how to build a project using a builder. You'd have to execute the builder and let it build the project to know if the wheel it generates is pure python or not.

As for setuptools:

There's a class that setuptools relies on to do the actual building of the Python project, called distutils.dist.Distribution which has a function named is_pure():

https://github.com/python/cpython/blob/e42b705188271da108de4...

Which makes sure that it doesn't have any known external modules or c libraries.

So to do detection of whether an sdist is a pure python, you'd have to execute setuptools and setup.py because of course setup.py isn't just configuration, it's full on Python.

So just looking at an sdist statically you can not know if the sdist is a pure python project or not.

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