Callable or not callable, that is the question!

Steven D'Aprano steve+comp.lang.python at pearwood.info
Fri Jul 12 11:49:14 CEST 2013


On Fri, 12 Jul 2013 07:36:30 +0000, Duncan Booth wrote:

> To be a convincing use-case you would have to show a situation where
> something had to be both a static method and a utility method rather
> than just one or the other and also where you couldn't just have both.

I have a class where I have a function that needs to be called both while 
the class is being constructed, and afterwards:

class Example:
    @staticmethod
    def do_stuff(arg):
        ...

    do_stuff(23)  # This doesn't work.

Example.do_stuff(42)


I have work-arounds: inside the class, I call do_stuff.__func__ instead 
of do_stuff, but really, that's ugly and distracting and merely a work-
around for the fact that staticmethods aren't callable. To make them 
callable is trivially easy: they just need a __call__ method that calls 
__func__ for you.



> If you can persuade me that you need _handle_bool as both a static
> method and a utility function, you probably also need to explain why you
> can't just use both:
> 
> class Parser:
>     def _handle_bool(input): ...
>     handle_bool = staticmethod(_handle_bool)

That's extremely inelegant. Why have two functions for something which is 
conceptually one?


-- 
Steven



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