[Python-ideas] staticmethod and classmethod should be callable

[Guido van Rossum]

+1 -- when we introduced these we didn't see the use case so clearly, but
it definitely exists.

On Wed, Jun 20, 2018 at 4:44 AM Steven D'Aprano <steve at pearwood.info> wrote:

> On Wed, Jun 20, 2018 at 11:56:05AM +0200, Jeroen Demeyer wrote:
> [...]
> > Since it makes sense to merge the classes "classmethod" and
> > "classmethod_descriptor" (PEP 579, issue 8), one of the above behaviors
> > should be changed. Given that adding features is less likely to break
> > stuff, I would argue that classmethod instances should become callable.
> [...]
> > Are there any reasons to *not* make staticmethod and classmethod
> callable?
>
> (The classes themselves are callable -- you're talking about the
> instances.)
>
> +1 yes please!
>
> The fact that classmethods and especially staticmethod instances aren't
> callable has been a long-running niggling pain for me. Occasionally I
> want to do something like this:
>
> class Spam:
>     @staticmethod
>     def utility(arg):
>         # something which is conceptually related to the Spam class
>         # but doesn't need a cls/self argument.
>         ...
>
>     value = utility(arg)
>
> but it doesn't work as staticmethod objects aren't callable until after
> they've gone through the descriptor protocol.
>
>
> I'm not the only one bitten by this:
>
>
> https://stackoverflow.com/questions/45375944/python-static-method-is-not-always-callable
>
> https://mail.python.org/pipermail/python-list/2011-November/615069.html
>
> Part of that thread, see links and discussion here:
>
> https://mail.python.org/pipermail/python-list/2011-November/615077.html
>
>
> I thought I had raised a bug report for this on the tracker, but my
> google-fu is failing me and I can't find it. But my recollection is that
> the simple fix is to make staticmethod.__call__ simply delegate to the
> underlying decorated function. And similar for classmethod.
>
> (Of course calling classmethod instances directly won't work unless you
> provide the class argument. But that's just a simple matter of bound
> versus unbound methods.)
>
>
> --
> Steve
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-- 
--Guido van Rossum (python.org/~guido)
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