[Python-Dev] About [].append == [].append

[Guido van Rossum]

I'm with Serhiy here, for mutable values I don't think the methods should
compare equal, even when the values do. For immutables I don't care either
way, it's an implementation detail.

On Thu, Jun 21, 2018, 12:55 Serhiy Storchaka <storchaka at gmail.com> wrote:

> 21.06.18 14:25, Jeroen Demeyer пише:
> > Currently, we have:
> >
> >  >>> [].append == [].append
> > False
> >
> > However, with a Python class:
> >
> >  >>> class List(list):
> > ....     def append(self, x): super().append(x)
> >  >>> List().append == List().append
> > True
>
> I think this is a bug. These bound methods can't be equal because they
> have different side effect.
>
> The use case for using "is" for __self__ is described by the OP of
> issue1617161. I don't know use cases for using "==".
>
> There is a related problem of hashing. Currently
> bound methods are not hashable if __self__ is not hashable. This makes
> impossible using them as dict keys.
>
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