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 <[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
