On Mon, Dec 1, 2008 at 8:21 PM, Filip Gruszczyński <[EMAIL PROTECTED]>wrote:
> I see. Thanks for a really good explanation, I like to know, how to do > things in the proper way :) I always prefer to use import module and then use module.function. The reason is simple. It makes the code more readable and maintainable. > > > 2008/12/1 Nick Craig-Wood <[EMAIL PROTECTED]>: > > Rafe <[EMAIL PROTECTED]> wrote: > >> On Dec 1, 7:26?am, "Filip Gruszczy?ski" <[EMAIL PROTECTED]> 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 <[EMAIL PROTECTED]> -- http://www.craig-wood.com/nick > > -- > > http://mail.python.org/mailman/listinfo/python-list > > > > > > -- > Filip Gruszczyński > -- > http://mail.python.org/mailman/listinfo/python-list >
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