Is "backporting" Python 3's `range` to Python 2 a bad idea?

One of my classes requires assignments to be completed in Python, and as an exercise, I've been making sure my programs work in both Python 2 and Python 3, using a script like this:

#!/bin/bash
# Run some PyUnit tests
python2 test.py
python3 test.py

One thing I've been doing is making range work the same in both versions with this piece of code:

import sys

# Backport Python 3's range to Python 2 so that this program will run
# identically in both versions.
if sys.version_info < (3, 0):
    range = xrange

Is this a bad idea?

EDIT:

The reason for this is that xrange and range work differently in Python 2 and Python 3, and I want my code to do the same thing in both. I could do it the other way around, but making Python 3 work like Python 2 seems stupid, since Python 3 is "the future".

Here's an example of why just using range isn't good enough:

for i in range(1000000000):
    do_something_with(i)

I'm obviously not using the list, but in Python 2, this will use an insane amount of memory.