Kristian Klette schrieb am 23.07.19 um 22:59:
> During the sprints after EuroPython, I made an attempt at adding support for
> comparing the results from `.values()` of two dicts.
>
> Currently the following works as expected:
>
> ```
> d = {'a': 1234}
>
> d.keys() == d.keys()
> d.items() == d.items()
> ```
>
> but `d.values() == d.values()` does not return the expected
> results. It always returns `False`. The symmetry is a bit off.
>
> In the bug trackers[0] and the Github PR[1], I was asked
> to raise the issue on the python-dev mailing list to find
> a consensus on what comparing `.values()` should do.
>
> I'd argue that Python should compare the values as expected here,
> or if we don't want to encourage that behaviour, maybe we should
> consider raising an exception.
> Returning just `False` seems a bit misleading.
>
> What are your thoughts on the issue?
FWIW, after reading most of this thread, I do not like the idea of raising
an exception for an innocent comparison. Just think of a list of arbitrary
objects, including a dict values view for some reason, and you're looking
for the right object in the list. Maybe in some kind of generic tool,
decorator, iter-helper, or whatever, something that has to deal with
arbitrary objects provided by random users, which uses "in" instead of a
loop with "is" comparisons.
I also kind-of like the idea of having
d.values() == d.values()
return True and otherwise let the comparison return False for everything
else. This seems to be the only reasonable behaviour that might(!) have a
use case, maybe in the same line as the argument above. I can't really see
a reason for implementing anything more than that.
Stefan
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