How to wrap a class's methods?

[Steven Bethard]

rbt wrote:
> Jeff Shannon wrote:
> 
>> You could probably also do this as a factory function, rather than as 
>> a class (also untested!):
>>
>> def Wrapper(func):
>>     def wrapped(self, *args, **kwargs):
>>         s, r = func(self, *args, **kwargs)
>>         if s != 'OK':
>>             raise NotOK((s,r))
>>         return r
>>     return wrapped
>>
>> I believe that this will be semantically almost equivalent, but 
>> conceptually slightly simpler.
>>
>> Jeff Shannon
> 
> This is a nice example. I have used sub-functions (functions within 
> functions) recently with some code, but I've wondered how proper it is 
> to do this. Is this type of thing frowned upon?

Nope.  If it was frowned upon, Python wouldn't support it. ;)  Sometimes 
it's even faster:

-------------------- test.py --------------------
def wrapper(func):
     def wrapped(*args, **kwargs):
         return bool(func(*args, **kwargs))
     return wrapped

class Wrapper(object):
     def __init__(self, func):
         self.func = func
     def __call__(self, *args, **kwargs):
         return bool(self.func(*args, **kwargs))
-------------------------------------------------

$ python -m timeit -s "import test; w = test.wrapper(sum)" "w([]); w([1,2])"
100000 loops, best of 3: 4.77 usec per loop

$ python -m timeit -s "import test; w = test.Wrapper(sum)" "w([]); w([1,2])"
100000 loops, best of 3: 6.52 usec per loop

Personally, I still tend towards the class-based version, but I'm sure 
in many cases the nested function version would work just as well.

STeVe