On 21.06.2018 23:40, Guido van Rossum wrote:
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.
In this light, methods rather shouldn't have a rich comparison logic at
all -- at the very least, until we have a realistic use case and can
flesh out the requirements for it.
In my previous message, I meant that if they do have that logic, the
right way is what `method_richcompare' does. And that was apparently
what the method's author (that you might be familiar with) was thinking
in
https://github.com/python/cpython/commit/47b9ff6ba11fab4c90556357c437cb4feec1e853
-- and even then and there, they were hesitant about the feature's
usefulness.
But Serhiy has just disproven that that is the right way which looks
like the final nail into its coffin.
On Thu, Jun 21, 2018, 12:55 Serhiy Storchaka <[email protected]
<mailto:[email protected]>> 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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--
Regards,
Ivan
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