Hello,
I hope not to bother anyone with a somewhat trivial question, I was
unable to get an answer from other channels.
I was just checking out some docs on ABCs for a project of mine, where
I need to do some type-related work. Those are the official docs about
the ValuesView type, in both Python 2 and 3:
https://docs.python.org/2/library/collections.html#collections.ValuesView
https://docs.python.org/3/library/collections.abc.html
and this is the source (Python 2, but same happens in Python 3)
https://hg.python.org/releases/2.7.11/file/9213c70c67d2/Lib/_abcoll.py#l479
I was very puzzled about the ValuesView interface, because from a
logical standpoint it should inherit from Iterable, IMHO (it's even
got the __iter__ Mixin method); on the contrary the docs say that it
just inherits from MappingView, which inherits from Sized, which
doesn't inherit from Iterable.
So I fired up my 2.7 interpreter:
>>> from collections import Iterable
>>> d = {1:2, 3:4}
>>> isinstance(d.viewvalues(), Iterable)
True
>>>
It looks iterable, after all, because of Iterable's own subclasshook.
But I don't understand why ValuesView isn't explicitly Iterable. Other
ABCs, like Sequence, are explicitly inheriting Iterable. Is there some
arcane reason behind that, or it's just a documentation+implementation
shortcoming (with no real-world impact) for a little-used feature?
Bye,
--
www.franzoni.eu - Twitter: @alanfranz
contact me at public@[mysurname].eu
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