Mark Dickinson <dicki...@gmail.com> added the comment:
To be precise, when doing `a < b`, either `a.__lt__` or `b.__gt__` can be used, since `__gt__` is considered the reversed / reflected version of `__lt__` (analogous to `__add__` and `__radd__`). >>> class A: ... def __lt__(self, other): return False ... >>> class B: ... def __gt__(self, other): return True ... >>> A() < B() False >>> B() < A() Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: '<' not supported between instances of 'B' and 'A' >>> sorted([A(), B()]) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: '<' not supported between instances of 'B' and 'A' >>> sorted([B(), A()]) [<__main__.B object at 0x10dc4cca0>, <__main__.A object at 0x10dc68ca0>] Presumably in the normal case, all the objects being sorted have the same type, and so in that case it's enough that the type implements at least one of __lt__ and __gt__. ---------- nosy: +mark.dickinson _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue39210> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
