Inconsistency: upper vs lower case inconsistency in platform.machine() on Windows-on-ARM vs Apple Silicon ARM64

[juj]

Bug report

Bug description:

import platform
print(platform.machine())

returns lowercase arm64 when run on Apple Silicon Mac M1, but uppercase ARM64 when run on Lenovo Qualcomm Snapdragon X IdeaCentre that is running Windows 11-on-ARM.

Is that intentional? Is that even fixable anymore without breaking? If not, this quirk might make sense to be documented in https://docs.python.org/3/library/platform.html#platform.machine

CPython versions tested on:

3.13

Operating systems tested on:

Windows

Linked PRs

• gh-138952: Document platform.machine() output casing inconsistency across platforms #138962
• [3.14] gh-138952: Document platform.machine() output casing inconsistency across platforms (GH-138962) #139045
• [3.13] gh-138952: Document platform.machine() output casing inconsistency across platforms (GH-138962) #139046

[emmatyping]

The platform.machine() output is system-dependent. As the title of the platform documentation states: "Access to underlying platform’s identifying data". Unfortunately there is no consistency with such data. For example, on a Linux machine platform.machine() results in "aarch64". I do agree it would be good to document explicitly the information from platform may not be consistent across platforms.

[ned-deily]

It's even more complicated in that the platform string returned can not nor should be used to determine things like CPU architecture based on parsing substrings. For example, macosx-26.0-arm64 and macosx-26.0-universal2 may both indicate that Python is running on an Apple Silicon (i.e. arm64) processor. In general, the string should only be used to test for equality. So we really shouldn't be encouraging trying to parse the string return for this purpose. While the docs sort of imply that, my suggestion we could improve the wording around that idea while not focusing on this particular example.

[juj]

These are all fine things to point out. It would be good for the documentation to establish this for the user, along with the recommended way to detect the CPU architecture. 👍

[ned-deily]

My apologies here for my somewhat off-topic comment. I was also reviewing a sysconfig.get_platform PR at the same time and was thinking of its output rather than the simpler output of platform.machine. The suggested PR with review comments should be fine.