New submission from Dan Snider <[email protected]>:
It doesn't even care if the result it gets from
ob.__getattribute__("__class__") isn't a type.
Surely `isinstance` is intended to do what it is named and be guaranteed to
return True if an object `ob` is an instance of class `cls`. There are already
ways to trick `isinstance` into thinking objects are instances of types not
present in its __mro__, ie with abstract base classes. All this does is
introduce the possibility of bugs.
`inspect.isclass` in particular is affected. If there's some obscure use case
for breaking `isinstance` in this manner, surely it shouldn't apply to
`inspect.isclass` which according to its documentation, "Return true if the
object is a class."
from inspect import isclass
class Liar:
def __getattribute__(self, attr):
if attr == '__class__':
return type
return object.__getattribute__(self, attr)
>>> islcass(Liar())
True
----------
components: Interpreter Core, Library (Lib)
messages: 310793
nosy: bup
priority: normal
severity: normal
status: open
title: isinstance is calling ob.__getattribute__ as a fallback instead of
object.__class__.__get__
versions: Python 3.7
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Python tracker <[email protected]>
<https://bugs.python.org/issue32683>
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