On Oct 17, 5:33 pm, Dave Angel <d...@davea.name> wrote: > On 10/17/2012 12:43 AM, Kevin Anthony wrote:> Is it not true that list > comprehension is much faster the the for loops? > > > If it is not the correct way of doing this, i appoligize. > > Like i said, I'm learing list comprehension.
> list comprehensions CAN be much faster, but not necessarily. The most > complex a loop, the less likely it'll help much. One-lining the comprehension seems to make a difference of about 10% out here. Maybe Ive missed something? Seems too large… # My original suggestion def dot(p,q): return sum (x*y for x,y in zip(p,q)) def transpose(m): return zip(*m) def mm(a,b): return mmt(a, transpose(b)) def mmt(a,b): return [[dot(ra, rb) for rb in b] for ra in a] # One-liner (Thanks Hans for reminding me of sum) def mm1(a,b): return [[sum([x*y for x,y in zip(ra,rb)]) for rb in zip(*b)] for ra in a] >>> t1=Timer("res=mm1(m,m)", setup="from __main__ import mm1, m") >>> t1.timeit(1000) 12.276363849639893 >>> t0=Timer("res=mm(m,m)", setup="from __main__ import mm, m") >>> t0.timeit(1000) 13.453603029251099 -- http://mail.python.org/mailman/listinfo/python-list