gh-140866: Document dict view == excludes non-set iterables - #155858
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gh-140866: Document dict view == excludes non-set iterables#155858SomSamantray wants to merge 1 commit into
== excludes non-set iterables#155858SomSamantray wants to merge 1 commit into
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… iterables collections.abc.Set.__eq__ requires the other operand to be a Set instance, so set-like dict views (keys()/items()) compare equal to another set/frozenset/view but always compare unequal to a list or tuple of the same elements. This is the one exception to the documented "set-like views accept any iterable as the other operand" rule for set operators, and it wasn't called out, leading to user confusion (pythongh-140866). Add the missing clarification plus a doctest example demonstrating the asymmetry.
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collections.abc.Set.__eq__only returns a real comparison when the otheroperand is itself a
Setinstance, sodict.keys()/dict.items()viewscompare equal to another set-like view,
set, orfrozenset, but alwayscompare unequal to a
listortupleof the same elements — even though thedocs say set-like views "accept any iterable as the other operand" for set
operators like
&,|, and^. That sentence doesn't carry over to==,and the docs never said so, which is why users keep reporting it as a bug.
This documents the exception right next to the existing sentence, and
extends the existing dictionary-view doctest example with two lines
demonstrating the asymmetry (
keys == ['bacon', 'spam']isFalse, butkeys == {'bacon', 'spam'}isTrue).Verified locally: the extended doctest block passes (10/10 examples), and a
full Sphinx build of
library/stdtypes.rst(sphinx-build -W --keep-going)produces no new warnings.
Fixes #140866
dict.keys(),dict.values()anddict.items()with==#140866