Re: 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
--
http://mail.python.org/mailman/listinfo/python-list