> Notwithstanding the "perverted" implementation, Alex's idea is
> absolutely wonderful and addresses a core usability issue with
> classmethods.
I'm not so sure. I think the main issue is that Python users aren't
used to static methods; C++ and Java users should be familiar with
them and I don't think they cause much trouble there.
> If only in the C API, I would like to see just such a universalmethod
> alternative to classmethod. That would allow different behaviors to be
> assigned depending on how the method is called.
>
> Both list.sort() and dict.fromkeys() would benefit from it:
>
>
> class MagicDict(dict):
>
> def _class_fromkeys(cls, lst, value=True):
> "Make a new dict using keys from list and the given value"
> obj = cls()
> for elem in lst:
> obj[elem] = value
> return obj
>
> def _inst_fromkeys(self, lst, value=True):
> "Update an existing dict using keys from list and the given value"
> for elem in lst:
> self[elem] = value
> return self
>
> newfromkeys = MagicDescriptor(_class_fromkeys, _inst_fromkeys)
>
> print MagicDict.newfromkeys('abc')
> print MagicDict(a=1, d=2).newfromkeys('abc')
But your _inst_fromkeys mutates self! That completely defeats the
purpose (especially since it also returns self) and I am as much
against this (approx. -1000 :-) as I am against sort() returning self.
To me this pretty much proves that this is a bad idea; such a schizo
method will confuse users more that a class method that ignores the
instance.
And if you made an honest mistake, and meant to ignore the instance,
it still proves that this is too confusing to do! :-)
--Guido van Rossum (home page: http://www.python.org/~guido/)
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