On Mon, Jul 07, 2014 at 04:52:17PM -0700, Ethan Furman wrote: > On 07/07/2014 04:49 PM, Benjamin Peterson wrote: > > > >Probably the best argument for the behavior is that "x is y" should > >imply "x == y", which preludes raising an exception. No such invariant > >is desired for ordering, so default implementations of < and > are not > >provided in Python 3. > > Nice. This bit should definitely make it into the doc patch if not already > in the docs.
However, saying this should not preclude classes where this is not the case, e.g. IEEE-754 NANs. I would not like this wording (which otherwise is very nice) to be used in the future to force reflexivity on object equality. https://en.wikipedia.org/wiki/Reflexive_relation To try to cut off arguments: - Yes, it is fine to have the default implementation of __eq__ assume reflexivity. - Yes, it is fine for standard library containers (lists, dicts, etc.) to assume reflexivity of their items. - I'm fully aware that some people think the non-reflexivity of NANs is logically nonsensical and a mistake. I do not agree with them. - I'm not looking to change anything here, the current behaviour is fine, I just want to ensure that an otherwise admirable doc change does not get interpreted in the future in a way that prevents classes from defining __eq__ to be non-reflexive. -- Steven _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
