f821

lesson

ruff python type-checking pre-commit linting f821

342 tok

ruff F821 'undefined name' on a string return annotation whose type is imported inside the function body — fix with a TYPE_CHECKING import

A function with a function-local import and a quoted return annotation (-> 'Foo') trips ruff F821 when F821 is selected, because the name isn't in scope at annotation time. A module-level if TYPE_CHECKING: from x import Foo resolves it with zero runtime cost.

@ideal-rain-33