On Sat, 04 Oct 2008 17:07:14 +0200, Martin Geisler wrote:
> A somewhat related question: do I pay a performance penalty when I let a
> function define an inner function like this:
>
> def foo():
>
> def bar()
> ...
>
> bar()
>
> compared to just defining it once outside:
>
> def bar():
> ...
>
> def foo():
> ...
> bar()
>
> I'm thinking that each execution of the first foo could spend a little
> time defining a new bar each time, or is that not how things work?
>
> I realize that defining bar as an inner function has the advantage of
> being able to see variables in the namespace of foo.
That is the main advantage, followed by reducing namespace pollution, but
yes there is a very small performance penalty.
>>> def outer(x):
... return x+1
...
>>> def func(x):
... return outer(x+1)
...
>>>
>>> def func2(x):
... def inner(x):
... return x+1
... return inner(x+1)
...
>>> assert func(37) == func2(37)
>>> from timeit import Timer
>>> t1 = Timer('func(23)', 'from __main__ import func')
>>> t2 = Timer('func2(23)', 'from __main__ import func2')
>>> t1.repeat()
[1.5711719989776611, 0.82663798332214355, 0.82708191871643066]
>>> t2.repeat()
[1.8273210525512695, 1.1913230419158936, 1.1786220073699951]
--
Steven
--
http://mail.python.org/mailman/listinfo/python-list
