[Python-Dev] Python semantic: Is it ok to replace not x == y with x != y? (no)

[Serhiy Storchaka]

On 15.12.15 15:04, Victor Stinner wrote:
> Should Python emit a warning when __eq__() is implemented but not __ne__()?

No. Actually I had removed a number of redundant (and often incorrect) 
__ne__ implementations after fixing object.__ne__.

> Should Python be modified to call "not __eq__()" when __ne__() is not
> implemented?

__ne__() always is implemented (inherited from object). Default __ne__ 
implementation calls __eq__() and negate it's result (if not 
NotImplemented).

But user class can define __ne__ with arbitrary semantic. That is the 
purpose of adding __ne__.