[pdonis]

In Python 2, itertools.imap will be faster since it doesn't realize a list. Also, if you are memory constrained, xrange doesn't realize a list either, whereas range does (but the article notes that range was slightly faster than xrange in his tests--I don't know if that's still true in Python 2, the article is 9 years old).

In Python 3, the map builtin is basically equivalent what itertools.imap was in Python 2, so it is the best choice. (Also, the range builtin in Python 3 no longer realizes a list.)

[pjscott]

I tried it with n=1000 and n=10000, and found that using xrange made it slightly faster, as did using itertools.imap, but the difference was pretty small.

(Here I'm using the stock Python 2.7.1 on a 2011 MacBook Pro.)

[pdonis]

using xrange made it slightly faster

That's what I would expect, since xrange works like a generator; but the internals of its implementation in CPython back when the article ran its original tests were evidently less efficient than they are now.

the difference was pretty small

I suspect that's because the strings being concatenated are really small (the largest will only be 5 bytes for n=10000). I would expect the difference to get bigger as the individual strings get larger.