How to loop backwards in python?

range() and xrange() take a third parameter that specifies a step. So you can do the following.

range(10, 0, -1)

Which gives

[10, 9, 8, 7, 6, 5, 4, 3, 2, 1] 

But for iteration, you should really be using xrange instead. So,

xrange(10, 0, -1)

Note for Python 3 users: There are no separate range and xrange functions in Python 3, there is just range, which follows the design of Python 2’s xrange.