Are all objects in Python equality-comparable?  I know that you can delete __hash__ to make an object unhashable (e.g., dicts).  If so, this is a great addition.

On Saturday, July 4, 2020 at 5:26:45 PM UTC-4, Joao S. O. Bueno wrote:


On Sat, 4 Jul 2020 at 16:51, Serhiy Storchaka <stor...@gmail.com> wrote:
30.06.20 18:58, Joao S. O. Bueno пише:
> I ended up writting an __eq__ - and in the process I found it is not
> _that_ straightforward  due
> to  having to check subclasses types when comparing.
> (given Base sequence A, child class B(A), class C(A) and class B1(B) -
> Instances of B and B1 can be
> equal, but instances of B and C should always be different) - or in
> Python, inside __eq__ :
>          if not issubclass(type(other), type(self)) and not
> issubclass(type(self), type(other)):
>              return False

It would be more correct to return NotImplemented.

Also, it is enough to test isinstance(other, type(self)) because
other.__eq__(self) be called first if the type of other is a subclass of
the type of self.

Ah - yes. Half the logic is already on the __eq__ semantics - thanks.
Well, I am updating that on my code right now. 

Anyway I am not seeing anyone opposing this going into col...abc.Sequence - 
Maybe it is ok for a BPO?  

(yes, there is this consideration I had, and also Guido,
that it would create new behavior in classes that already exist, but I saw
 no way that could break code not specially crafted to  break with this change.)


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