Larry Bates <[EMAIL PROTECTED]> wrote: > Note: if lists are long take a look at itertools izip. zip creates > a list of lists which could take lots of memory/time if they are VERY > large. itertools izip iterates over them in place.
That's interesting. I was going to quibble with the assertion that zip could take lots of time, since on the face of it a loop using izip packs and unpacks just as many tuples. Fortunately I tried it out before claiming that zip would be just as fast :) It would appear that even for short sequences the izip solution is faster. My guess would be it is because the same tuple objects are being reused in the izip version. C:\Python25\Lib>timeit.py -s "a, b, c = [range(1000)]*3" -s "from itertools import izip" "for p,q,r in izip(a,b,c): pass" 10000 loops, best of 3: 131 usec per loop C:\Python25\Lib>timeit.py -s "a, b, c = [range(1000)]*3" "for p,q,r in zip(a,b,c): pass" 1000 loops, best of 3: 212 usec per loop C:\Python25\Lib>timeit.py -s "a, b, c = [range(100)]*3" -s "from itertools import izip" "for p,q,r in izip(a,b,c): pass" 100000 loops, best of 3: 13.9 usec per loop C:\Python25\Lib>timeit.py -s "a, b, c = [range(100)]*3" "for p,q,r in zip(a,b,c): pass" 10000 loops, best of 3: 22.6 usec per loop C:\Python25\Lib>timeit.py -s "a, b, c = [range(10)]*3" -s "from itertools import izip" "for p,q,r in izip(a,b,c): pass" 100000 loops, best of 3: 2.21 usec per loop C:\Python25\Lib>timeit.py -s "a, b, c = [range(10)]*3" "for p,q,r in zip(a,b,c): pass" 100000 loops, best of 3: 3.52 usec per loop -- http://mail.python.org/mailman/listinfo/python-list
