New submission from Serhiy Storchaka <storchaka+cpyt...@gmail.com>:
According to the documentation [1] abstract classes collections.abc.Set and collections.abc.Mapping provide mixin method __ne__. But implementations of __ne__ in these classes were removed in 3.4 (see issue21408), so the default implementation is inherited from object. The reason is that it works better with classes which override __ne__ to return non-boolean, e.g. NumPy, SymPy and sqlalchemy classes. Previously the != operator falled back to other__eq__(), now it falls back to other__ne__(). [1] https://docs.python.org/3/library/collections.abc.html#collections-abstract-base-classes But now we have a discrepancy between the decomentation and the code. According to the documentation, if we have a class which inherits from both Set and int, in that order, the __ne__ method should be inherited from class Set instead of class int. But currently it is inherited from int. >>> import collections.abc >>> class A(collections.abc.Set, int): pass ... >>> A.__ne__ <slot wrapper '__ne__' of 'int' objects> One way to solve this -- remove __ne__ from lists of mixin methods (see issue41400). Other way -- add the __ne__ implementations which are identical to the default implementation but has preference in the inheritance. I prefer the latter. ---------- components: Library (Lib) messages: 374470 nosy: rhettinger, serhiy.storchaka priority: normal severity: normal status: open title: Restore default implementation of __ne__ in mixins Set and Mapping type: behavior versions: Python 3.10 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue41416> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
