invoke method on many instances

[Simon Forman]

On Jul 20, 3:29 am, "Gabriel Genellina" <gagsl-... at yahoo.com.ar>
wrote:
> En Sat, 18 Jul 2009 12:31:46 -0300, Alan G Isaac <alan.is... at gmail.com>  
> escribió:
>
> >> On Fri, 17 Jul 2009 05:19:50 +0000, Alan G Isaac wrote:
> >>> def apply2(itr, methodname, *args, **kwargs):
> >>>     f = operator.methodcaller(methodname, *args, **kwargs)
> >>>     for item in itr:
> >>>         f(item)
>
> > On 7/17/2009 3:45 AM Steven D'Aprano apparently wrote:
> >> for obj in objects:
> >>     getattr(obj, methodname)(*args, **kwargs)
>
> > Are there any obvious considerations in choosing
> > between those two?
>
> The operator.methodcaller version is faster in my tests for large  
> collections, but slightly slower when you have very few elements.
>
> <code>
> import operator
> import timeit
>
> class X:
>    def method(self, x, y, **kw): pass
>
> def apply1(itr, methodname, *args, **kwargs):
>      for item in itr:
>          getattr(item, methodname)(*args, **kwargs)
>
> def apply2(itr, methodname, *args, **kwargs):
>      f = operator.methodcaller(methodname, *args, **kwargs)
>      for item in itr:
>          f(item)
>
> L=[X() for _ in range(3000)]
> apply1(L,'method', 1, 2, foo=3)
> apply2(L,'method', 1, 2, foo=3)
>
> timeit.timeit(setup="from __main__ import apply1,apply2,L",  
> stmt="apply1(L,'method', 1, 2, foo=3)", number=1000)
> timeit.timeit(setup="from __main__ import apply1,apply2,L",  
> stmt="apply2(L,'method', 1, 2, foo=3)", number=1000)
> </code>
>
> --
> Gabriel Genellina

If your instances are all of the same class you can pass in the method
directly like so:

def apply3(iterator, method, *args, **kwargs):
    for item in iterator:
        method(item, *args, **kwargs)

class X:
   def method(self, x, y, **kw): pass

items = [X() for _ in range(10)]

apply3(items, X.method, 1, 2, foo=3)

HTH,
~Simon