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Proposed warning: assert <generator_expression> #534
Description
For example:
assert (result[i] == expected[i] for i in range(len(expected)))
assert (result[key] == expected[key] for key in result.keys() | expected.keys())bugbear could warn and suggest adding all().
Note that even an empty generator expression is truey:
assert (False for _ in range(0))so it's fine that bugbear doesn't statically know the length of the generator.
There are a couple of similar warnings:
- F631 is a similar rule for
assert <tuple>. - Proposal (2) in Couple new rule suggestions #440 is a similar rule for
assert <constant>.
Activity
JelleZijlstra commentedon Dec 17, 2025
Seems useful!
This could even be added to Python itself as a SyntaxWarning.
cooperlees commentedon Dec 23, 2025
Sounds good to me too ... Thanks for the PR too. Will check it out.
cooperlees commentedon Sep 9, 2026
Merged a partial solution - we wonder if it would make sense to broaden this into asserts with other constructs that we can statically detect will always be true, such as nonempty list literals ...
B044: report asserts on other always-true values