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bpo-32996: Documentation fix-up. (GH-16646) 

PR #4906 changed the typing.Generic class hierarchy, leaving an
outdated comment in the library reference. User-defined Generic ABCs now
must get a abc.ABCMeta metaclass from something other than typing.Generic
inheritance.
This commit is contained in:
M. Eric Irrgang 2019-10-10 14:11:33 +03:00 committed by Ivan Levkivskyi
parent a05fcd3c7a
commit d47f0dd2e8
1 changed files with 4 additions and 3 deletions
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Doc/library/typing.rst
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@ -307,9 +307,10 @@ User defined generic type aliases are also supported. Examples::
def inproduct(v: Vec[T]) -> T: # Same as Iterable[Tuple[T, T]]
return sum(x*y for x, y in v)
The metaclass used by :class:`Generic` is a subclass of :class:`abc.ABCMeta`.
A generic class can be an ABC by including abstract methods or properties,
and generic classes can also have ABCs as base classes without a metaclass
.. versionchanged:: 3.7
:class:`Generic` no longer has a custom metaclass.
A user-defined generic class can have ABCs as base classes without a metaclass
conflict. Generic metaclasses are not supported. The outcome of parameterizing
generics is cached, and most types in the typing module are hashable and
comparable for equality.