On Fri, Jan 24, 2020 at 3:45 AM Steven D'Aprano <st...@pearwood.info> wrote:
> On Fri, Jan 24, 2020 at 12:36:13PM +0300, Ivan Pozdeev via Python-Dev > wrote: > > > >I'm tempted to declare this implementation-defined behavior -- > *implicit* > > >calls to __eq__ and __ne__ *may* be skipped if both sides are the same > > >object depending on the whim of the implementation. > > > > This cannot be an implementation detail because it changes the outcome > of > > operations. > > Guido didn't call it an implementation *detail* but implementation- > defined behaviour. And of course that implies that the outcome could be > different when using different implementations. > > I'm pretty sure Guido understood the implication when he made that > comment. > Yes I did. The only thing I'm unsure of here is whether direct use of the `==` and > `!=` operators are included as "implicit calls" to the dunders. I > *think* I understand Guido's intention, but I'm not sure: > > * x == y MUST call `__eq__` > > * likewise x != y MUST call `__ne__` > > * but compound objects such as lists and other collections MAY skip > calling `__eq__` (or `__eq__`) on their component parts. > Right. -- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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