Hi. As of python 3, behavior of object.__ne__ changed to call (not object.__eq__) if implemented. This changement can be seen in function object_richcompare in file Objects/typeobject.c.

Documentation didn't change though, still saying[1] that "There are no implied relationships among the comparison operators. [...] Accordingly, when defining __eq__(), one should also define __ne__()".

Maybe a paragraph about this new behavior would be fine? I am not sure if last sentence of last paragraph is what it means, but it was already there in python 2 doc so guess no. I am not sure about how to write it so no patch, sorry.

[1] http://docs.python.org/3.3/reference/datamodel.html#object.__eq__

There's a (long-standing) issue already open for this: #4395.  I'll close this as a duplicate and add a note to that issue;  with any luck, pinging that issue might produce some movement.

nosy: + mark.dickinson
messages: + msg181629

superseder: Document auto __ne__ generation; provide a use case for non-trivial __ne__
resolution: duplicate