Loop backwards using indices in Python?

Question

I am trying to loop from 100 to 0. How do I do this in Python?

for i in range (100,0) doesn't work.

Answer 1

Try range(100,-1,-1), the 3rd argument being the increment to use.

Answer 2

for i in range(100, -1, -1)

and some slightly longer (and slower) solution:

for i in reversed(range(101))

for i in range(101)[::-1]

Answer 3

In my opinion, this is the most readable:

for i in reversed(xrange(101)):
    print i,

Answer 4

Generally in Python, you can use negative indices to start from the back:

numbers = [10, 20, 30, 40, 50]
for i in xrange(len(numbers)):
    print numbers[-i - 1]

Result:

50
40
30
20
10