Delaney, Timothy (Tim) wrote: > Devan L wrote: > >>Map is in C. It's faster, but not as clear. Some people do think >>map(f, L) is nicer though. Google is your friend here, if you want to >>read the old arguments. > > map() will be faster if the function you are calling from map() is > *also* in coded in C. If it's coded in python, then the generator > expression will probably be faster. > > Use whatever reads better to you. Look at optimising when you need to, > and not before.
While I fully agree with your conclusion, I don't think it's right to say that a Python-coded function in a list comprehension will be faster than the corresponding map. Consider: > python -m timeit -s "r = xrange(1000); f = lambda x: 10*x" "map(f, r)" 1000 loops, best of 3: 707 usec per loop > python -m timeit -s "r = xrange(1000); f = lambda x: 10*x" "[f(i) for i in r]" 1000 loops, best of 3: 749 usec per loop However, when a list comprehension allows you to inline a function, it's almost certainly going to be faster: C:\Documents and Settings\steve>python -m timeit -s "r = xrange(1000)" "[10*i for i in r]" 1000 loops, best of 3: 300 usec per loop STeVe -- http://mail.python.org/mailman/listinfo/python-list
