[Tutor] optimization: faster than for

[elis aeris]

I found this on the net, and it's a different arrangement to using for

the author claims it will result in faster performance, but i can't find
documents on it, because I can't figure out which parts are parameters and
which parts on special words, for python.
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The operations with explicit loop counters have to be translated into Python byte code and must be interpreted. Implicit loop counter can be incremented by the core code (translated from C sources). Try this:

import timeit

sWhile = """\
x = 0
y = 0
number_scanned = 0
while x < 1024:
    while y < 768:
        y = y + 1
        number_scanned = number_scanned + 1
    y = 0
    x = x + 1
"""
t = timeit.Timer(stmt=sWhile)
print "%.2f usec/pass" % (1000000 * t.timeit(number=10)/10)


sFor = """\
number_scanned = 0
for x in xrange(1024):
    for y in xrange(768):
        number_scanned = number_scanned + 1
"""
t = timeit.Timer(stmt=sFor)
print "%.2f usec/pass" % (1000000 * t.timeit(number=10)/10)


The sWhile and sFor are the multiline strings containing the equivalent code written using while and for loop respectively.