Starting with version 3.9.5 platform.win32* functions have been re-written and consume STDIN. The bug comes down to running 'ver', 'command /c ver', 'cmd /c ver' in platform._syscmd_ver() via subprocess.check_output().

The following code demonstrate the problem:

Python\396\python -c "import platform as p, sys;print(sys.stdin.tell());p.win32_ver();print(sys.stdin.tell())" < file
0
8000

All functions dependent on platform._syscmd_ver(), including platform.uname(), consume STDIN.

This behavior breaks all the scripts on Windows platform that have the calls mentioned above and use the following invocation:

python script.py < file

The obvious fix is to add "stdin=subprocess.DEVNULL" argument to check_output() call.

Would you like to create a pull request to that effect?

I will try

Well, I opened pull request, but it was closed. You guys have a very good team work going on out there :) Good luck!

The pull request you opened was invalid, because it was just trying to merge the `main` branch of the python/cpython repository into the `3.9` branch.  What we need instead is a pull request between a branch from `main` in your own fork of python/cpython with the change you want to see in a new commit.  You can find a more detailed walkthrough in the devguide, or if you prefer to leave it for someone else to do that is also a valid option :)

I do not understand why a one line change in the code requires full blown git clone. Shouldn't you guys have a system that allows to change code over the web interface and your bots will do the rest: checks, tests, regressions, etc.?

You can make a PR entirely through the Github web interface, though we do generally encourage running the tests locally, especially since it would be good to add a new test for this case.

New changeset 0ee0a740e12ec8568aafa033aa6bb08b265afe26 by Konstantin-Glukhov in branch 'main':
bpo-44572: On Windows, disconnect STDIN in platform._syscmd_ver() to prevent erroneous STDIN consumption (GH-27092)
https://github.com/python/cpython/commit/0ee0a740e12ec8568aafa033aa6bb08b265afe26

New changeset 425756abdc03263ab3a52b068befd1ddb16c2dd2 by Miss Islington (bot) in branch '3.10':
bpo-44572: On Windows, disconnect STDIN in platform._syscmd_ver() to prevent erroneous STDIN consumption (GH-27092) (GH-27124)
https://github.com/python/cpython/commit/425756abdc03263ab3a52b068befd1ddb16c2dd2

New changeset 5fc784e28ab9cd02c30395d1973ff825b787efa2 by Miss Islington (bot) in branch '3.9':
bpo-44572: On Windows, disconnect STDIN in platform._syscmd_ver() to prevent erroneous STDIN consumption (GH-27092)
https://github.com/python/cpython/commit/5fc784e28ab9cd02c30395d1973ff825b787efa2

Thanks for the contribution!