bpo-19072: Update descriptor howto for decorator chaining (GH-22934)

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Raymond Hettinger 2020-10-23 18:37:27 -07:00 committed by GitHub
parent 04523c5bd6
commit 8e5b0fdce3
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1 changed files with 13 additions and 3 deletions

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@ -872,6 +872,16 @@ Using the non-data descriptor protocol, a pure Python version of
def __get__(self, obj, cls=None):
if cls is None:
cls = type(obj)
def newfunc(*args):
return self.f(cls, *args)
return newfunc
if hasattr(obj, '__get__'):
return self.f.__get__(cls)
return types.MethodType(self.f, cls)
The code path for ``hasattr(obj, '__get__')`` was added in Python 3.9 and
makes it possible for :func:`classmethod` to support chained decorators.
For example, a classmethod and property could be chained together::
class G:
@classmethod
@property
def __doc__(cls):
return f'A doc for {cls.__name__!r}'