New submission from Dutcho <[email protected]>:
While `Flag() in Flag()` and `Flag() | Flag()` result in the expected outcomes,
e.g. `str() in Flag()` unexpectedly returns `True`, whereas `Flag() | str()` as
expected raises a TypeError.
>>> import enum
>>> ABC = enum.Flag('ABC', 'a, b, c')
>>> ac = ABC.a | ABC.c
>>> def test():
... for x in (*ABC, 'test'):
... print(x, end=' ')
... try:
... print(x in ac, end=' ')
... except TypeError as e:
... print(e, end=' ')
... try:
... print(x | ac)
... except TypeError as e:
... print(e)
>>> test()
ABC.a True ABC.c|a
ABC.b False ABC.c|b|a
ABC.c True ABC.c|a
test True unsupported operand type(s) for |: 'str' and 'ABC'
Likely cause is modelling of Flag.__contains__ after Flag.__and__ etc., which
is incorrect as __contains__ doesn't have a reflected version like __and__ etc.
have. The returned `NotImplemented` is therefore not handled by the
interpreter, although it is converted to bool to satisfy __contains__ return
type.
This can be fixed by redefinition of Flag.__contains__ to raise TypeError:
>>> def __contains__(self, other):
... if not isinstance(other, self.__class__):
... raise TypeError(f"unsupported operand type(s) for 'in': "
... f"{type(other).__qualname__!r} and
{type(self).__qualname__!r}")
... return other & self == other
>>> enum.Flag.__contains__ = __contains__
>>> test()
ABC.a True ABC.c|a
ABC.b False ABC.c|b|a
ABC.c True ABC.c|a
test unsupported operand type(s) for 'in': 'str' and 'ABC' unsupported
operand type(s) for |: 'str' and 'ABC'
----------
components: Library (Lib)
messages: 314890
nosy: Dutcho
priority: normal
severity: normal
status: open
title: x in enum.Flag() is True when x is no Flag
type: behavior
versions: Python 3.6
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Python tracker <[email protected]>
<https://bugs.python.org/issue33217>
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