New submission from Max: I think collections.abc.Hashable.__subclasshook__ should check __eq__ method in addition to __hash__ method. This helps detect classes that are unhashable due to:
to __eq__ = None Of course, it still cannot detect: def __eq__: return NotImplemented but it's better than nothing. In addition, it's probably worth documenting that explicitly inheriting from Hashable has (correct but unexpected) effect of *suppressing* hashability that was already present: from collections.abc import Hashable class X: pass assert issubclass(X, Hashable) x = X() class X(Hashable): pass assert issubclass(X, Hashable) x = X() # Can't instantiate abstract class X with abstract methods ---------- assignee: docs@python components: Documentation, Interpreter Core messages: 291382 nosy: docs@python, max priority: normal severity: normal status: open title: Hashable doesn't check for __eq__ _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue30026> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
