Monkeypatching a staticmethod?

[Ian Kelly]

On Thu, Jan 9, 2014 at 10:23 PM, Roy Smith <roy at panix.com> wrote:
> This is kind of surprising.  I'm running Python 2.7.1.  I've got a class
> with a staticmethod that I want to monkeypatch with a lambda:
>
> ----------------------------------
> class Foo:
>     @staticmethod
>     def x():
>         return 1
>
> Foo.x = lambda: 2
> print Foo.x()
> ----------------------------------
>
> What's weird is that it seems to remember that x is a staticmethod
> despite having been patched:
>
> Traceback (most recent call last):
>   File "static.py", line 8, in <module>
>     Foo.x()
> TypeError: unbound method <lambda>() must be called with Foo instance as
> first argument (got nothing instead)

No, if it were still a staticmethod then the call would work without
error.  That error is the same that you would get in Python 2 if you
defined the function directly in the class without the staticmethod
decorator.  (In Python 3 the call succeeds as long as it's made from
the class and not from an instance).

> What seems to work is to patch it with another staticmethod:
>
> ----------------------------------
> class Foo:
>     @staticmethod
>     def x():
>         return 1
>
> @staticmethod
> def x():
>     return 2
>
> Foo.x = x
> print Foo.x()
> ----------------------------------
>
> $ python static.py
> 2
>
> I didn't even know you could define a staticmethod outside of a class!

I suggest defining x as a normal function and writing the assignment
as "Foo.x = staticmethod(x)" to keep x callable from the global
namespace.  Or just del it after doing the monkey patch.