On Tue, 01 Nov 2005 00:24:37 GMT, "Giovanni Bajo" <[EMAIL PROTECTED]> wrote:
>Hello,
>
>what's the magic needed to reuse the base-class implementation of a
>classmethod?
>
>class A(object):
> @classmethod
> def foo(cls, a,b):
> # do something
> pass
>
>class B(A):
> @classmethod
> def foo(cls, a, b):
> A.foo(cls, a, b) # WRONG!
>
>I need to call the base-class classmethod to reuse its implementation, but I'd
>like to pass the derived class as first argument.
>--
>Giovanni Bajo
>
>
Maybe define a funny-class-method decorator?
(nothing below tested beyond what you see ;-)
>>> def funnycm(m):
... return property(lambda cls: m.__get__(type(cls), type(type(cls))))
...
>>> class A(object):
... @funnycm
... def foo(cls, a, b):
... print cls, a, b # do something
...
>>> class B(A):
... pass # just inherit
...
>>> a=A()
>>> a.foo(1,2)
<class '__main__.A'> 1 2
>>> b=B()
>>> b.foo(1,2)
<class '__main__.B'> 1 2
Or more directly, a custom descriptor (with dynamic method replacement for good
measure ;-)
>>> class funnycm(object):
... def __init__(self, f): self._f = f
... def __get__(self, inst, cls=None):
... return self._f.__get__(inst is None and cls or type(inst))
... def __set__(self, inst, m): self._f = m # replace method
...
>>> class A(object):
... @funnycm
... def foo(cls, a, b):
... print cls, a, b # do something
...
>>> class B(A):
... pass # just inherit
...
>>> a=A()
>>> a.foo(1,2)
<class '__main__.A'> 1 2
>>> b=B()
>>> b.foo(1,2)
<class '__main__.B'> 1 2
>>> A.foo(3,4)
<class '__main__.A'> 3 4
>>> B.foo(3,4)
<class '__main__.B'> 3 4
>>> a.foo = lambda cls, *args: repr(args)
>>> a.foo('what','now','then?')
"('what', 'now', 'then?')"
>>> b.foo('eh?')
"('eh?',)"
>>> B.foo()
'()'
Vary to taste ;-)
Regards,
Bengt Richter
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