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Reflect it that sys.lazy_modules is no longer a flat set #145057
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Hi @johnslavik — I noticed this issue is self-assigned.
If you’re actively working on it, I’ll hold off. If not, I’d be happy to help with updating tests and docsI'm working on that, but thanks for chiming in!
- added a commit that references this issue
on Mar 27, 2026 - added a parent issue
on Apr 14, 2026
Bug report
Bug description:
sys.lazy_modulesis now adict[str, set[str]], not a flat set. There's some places in the stdlib code that incorrectly suggests the older invariant.Most notable example:
cpython/Lib/test/test_import/test_lazy_imports.py
Lines 457 to 459 in 70da972
The PEP needs updating as well -- https://peps.python.org/pep-0810/#lazy-import-mechanism -- @DinoV, I think this is something you were working on, or is it open for contrib?
I'm happy to pick this one up (i.e. fixing our code to reflect
sys.lazy_modulesis a dict) if you'd like that! (Please reassign otherwise.)cc @pablogsal @DinoV @brittanyrey @Yhg1s
CPython versions tested on:
CPython main branch
Operating systems tested on:
No response
Linked PRs
sys.lazy_modulesis a dict, not a set #146084