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unreliable-callable-check (B004)#

Derived from the flake8-bugbear linter.

Fix is sometimes available.

What it does#

Checks for uses of hasattr to test if an object is callable (e.g., hasattr(obj, "__call__")).

Why is this bad?#

Using hasattr is an unreliable mechanism for testing if an object is callable. If obj implements a custom __getattr__, or if its __call__ is itself not callable, you may get misleading results.

Instead, use callable(obj) to test if obj is callable.


hasattr(obj, "__call__")

Use instead: