New submission from xitop <reg.b...@poti.sk>:
The `dict.__contains()` function does not fully comply with the description in
the "Data Model" section of the official documentation, which states:
"__contains__(self, item) ... Should return true if item is in self, false
otherwise."
Basically the same is written in "Mapping Types - dict": "key in d - Return
True if d has a key key, else False."
According to that, testing a presence of an unhashable object in a dict should
return False. But it raises a TypeError instead.
Example:
>>> () in {}
False
but:
>>> [] in {}
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'
There is a related SO question:
https://stackoverflow.com/questions/48444079/unexpected-behaviour-of-dictionary-membership-check
currently without a clear answer whether it is a bug or desired behaviour
supposed to expose programming errors. In the latter case, it seems to be not
documented.
----------
components: Interpreter Core
messages: 310751
nosy: xitop
priority: normal
severity: normal
status: open
title: dict.__contains__(unhashable) raises TypeError where False was expected
versions: Python 3.6
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue32675>
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