[issue26973] Dict View binops permit non-set types
Joshua Morton added the comment: There (seemed to be) consensus between the one or two on topic commenters that something was off, although much of the discussion was on a tangent. Although on looking back, there was even less discussion than I originally thought. Heh. My response was going to be very different, however I did some additional digging: the `collections.abc.Set` class can be used as a mixin for implementing set-likes. In its default implementations of the various binops, they will attempt to convert the right hand argument of an operator to the correct type, via _from_iterable. This in effect makes the set the special case that is more permissive than Set is. This strikes me as strange, I'd expect set and Set to be 'the same', or in other words a Set to act like a set and vice versa. But it seems that python swings toward your intuition and not mine. And the opposite, making set *more* permissive also doesn't sit well, nor does it feel necessary. -- ___ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue26973> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue26973] Dict View binops permit non-set types
New submission from Joshua Morton:
Following the comments in python ideas [1], I'm submitting a bug report. In
python 3, dictionary views (KeysView and ItemsView specifically) do not adhere
to the same interface as Sets. Specifically, the __and__, __or__, __xor__, and
__sub__ methods on Views will accept a non-set type (`{}.keys() | []`), while
the same throws a TypeError on a Set. The suggested, not-backwards-compatible
solution, was to have dictviews raise errors in the same way.
[1] https://mail.python.org/pipermail/python-ideas/2016-April/039469.html
--
messages: 265110
nosy: Joshua Morton
priority: normal
severity: normal
status: open
title: Dict View binops permit non-set types
type: behavior
versions: Python 3.4, Python 3.5
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