https://docs.python.org/3/whatsnew/3.0.html#views-and-iterat...
My Python is rusty, but I actually had to go look up the differences - my initial thought was "I'm pretty sure it used to be that range() generated a list and xrange() basically just iterated a value, but at some point range() was changed to use the xrange() behavior - I'd have to look it up to give you more detail than that." I didn't realize that xrange() had been completely removed from 3.x, for example. For that matter, I was thinking that both of them might have existed in 1.x, though it looks like they were added in 2.0.
http://pythoncentral.io/how-to-use-pythons-xrange-and-range/
From that article (buried near the end for some reason):
>One more thing to add. In Python 3.x, the xrange function does not exist anymore. The range function now does what xrange does in Python 2.x, so to keep your code portable, you might want to stick to using range instead.