Do more imported objects affect performance

[Filip Gruszczyński]

I see. Thanks for a really good explanation, I like to know, how to do
things in the proper way :)

2008/12/1 Nick Craig-Wood <nick at craig-wood.com>:
> Rafe <rafesacks at gmail.com> wrote:
>>  On Dec 1, 7:26?am, "Filip Gruszczy?ski" <grusz... at gmail.com> wrote:
>> > I have following question: if I use
>> >
>> > from module import *
>> >
>> > instead
>> >
>> > from module import Class
>> >
>> > am I affecting performance of my program? I believe, that all those
>> > names must be stored somewhere, when they are imported and then
>> > browsed when one of them is called. So am I putting a lot of "garbage"
>> > to this storage and make those searches longer?
>>
>>  Why use it if you don't need it? Your post implies a choice and the
>>  '*' import can really make things muddy if it isn't actually necessary
>>  (rare). Why not just import the module and use what you need? It is
>>  way easier to read/debug and maintains the name-space.
>
> Importing the module is actualy slower...  If you import the name into
> your namespace then there is only one lookup to do.  If you import the
> module there are two.
>
> $ python -m timeit -s 'from timeit import Timer' 'Timer'
> 10000000 loops, best of 3: 0.0784 usec per loop
>
> $ python -m timeit -s 'import timeit' 'timeit.Timer'
> 1000000 loops, best of 3: 0.243 usec per loop
>
> I'm not suggestion you should ever use "from module import *" only
> ever import the things you actually need, eg
> "from module import MyClass, my_function"
>
> And here is the test again, actually calling something with the same
> difference in execution speed :-
>
> $ python -m timeit -s 'from os import nice' 'nice(0)'
> 1000000 loops, best of 3: 1.21 usec per loop
>
> $ python -m timeit -s 'import os' 'os.nice(0)'
> 1000000 loops, best of 3: 1.48 usec per loop
>
> --
> Nick Craig-Wood <nick at craig-wood.com> -- http://www.craig-wood.com/nick
> --
> http://mail.python.org/mailman/listinfo/python-list
>



-- 
Filip Gruszczyński