Decorating class member functions

[Virgil Dupras]

On May 3, 9:21 pm, Andy Terrel <andy.ter... at gmail.com> wrote:
> Okay does anyone know how to decorate class member functions?
>
> The following code gives me an error:
>
> Traceback (most recent call last):
>   File "decorators2.py", line 33, in <module>
>     s.update()
>   File "decorators2.py", line 13, in __call__
>     retval = self.fn.__call__(*args,**kws)
> TypeError: update() takes exactly 1 argument (0 given)
>
> ------------------
>
> #! /usr/bin/env python
>
> class Bugger (object):
>     def __init__ (self, module, fn):
>         self.module = module
>         self.fn = fn
>
>     def __call__ (self,*args, **kws):
>         ret_val = self.fn(*args,**kws)
>         return ret_val
>
> def instrument (module_name):
>     ret_val = lambda x: Bugger(module_name, x)
>     return ret_val
>
> class Stupid:
>     def __init__(self):
>         self.val = 1
>
>     @instrument("xpd.spam")
>     def update(self):
>         self.val += 1
>
> s = Stupid()
> s.update()

A decorator is a function that takes one single parameter: a function.
"instrument" must return a decorator.