Question

We can do numeric iteration like:

for i in xrange(10):
    print i,

and in C-style:

i = 0
while i < 10:
    print i,
    i = i + 1

Yes, I know, the first one is less error-prone, more pythonic but is it fast enough as C-style version?

PS. I’m from C++ planet and pretty new on Python one.

Answer 1

I am sure the while version is slower. Python will have to lookup the add operation for the integer object on each turn of the loop etc, it is not pure C just because it looks like it!

And if you want a pythonic version of exactly the above, use:

print " ".join(str(i) for i in xrange(10))

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Edit: My timings look like this. This is just a silly running loop without printing, just to show you what writing out “i += 1” etc costs in Python.

$ python -mtimeit "i=0" "while i < 1000: i+=1"
1000 loops, best of 3: 303 usec per loop
$ python -mtimeit "for i in xrange(1000): pass"
10000 loops, best of 3: 120 usec per loop