New submission from Géry <[email protected]>:
With the current Python equivalent `ClassMethod` implementation of
`classmethod` given in Raymond Hettinger's _Descriptor HowTo Guide_, the
following code snippet:
```
class A:
@ClassMethod
def f(cls, *, x): pass
print(A.f)
A.f(x=3)
```
prints:
> <function ClassMethod.\_\_get\_\_.<locals>.newfunc at 0x106b76268>
and raises:
> TypeError: newfunc() got an unexpected keyword argument 'x'
instead of only printing:
> <bound method A.f of <class '\_\_main\_\_.A'>>
like the `@classmethod` decorator would do.
So the `ClassMethod` implementation fails in two regards:
* it does not return a bound method to a class;
* it does not handle keyword-only arguments.
With this PR `ClassMethod` will correctly emulate `classmethod`. This approach
(`types.MethodType`) is already used in the Python equivalent `Function`
implementation of functions given earlier in the same guide.
----------
assignee: docs@python
components: Documentation
messages: 345031
nosy: docs@python, eric.araujo, ezio.melotti, maggyero, mdk, rhettinger,
willingc
priority: normal
pull_requests: 13785
severity: normal
status: open
title: Correct classmethod emulation in Descriptor HowTo Guide
type: behavior
versions: Python 3.7
_______________________________________
Python tracker <[email protected]>
<https://bugs.python.org/issue37203>
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