Python range() with negative strides

Question

Is there a way of using the range() function with stride -1?

E.g. using range(10, -10) instead of the square-bracketed values below?

I.e the following line:

for y in range(10,-10)

Instead of

for y in [10,9,8,7,6,5,4,3,2,1,0,-1,-2,-3,-4,-5,-6,-7,-8,-9,-10]:

Obviously one could do this with another kind of loop more elegantly but the range() example would work much better for what I want.

Answer 1

You can specify the stride (including a negative stride) as the third argument, so

range(10,-11,-1) 

gives

[10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, -1, -2, -3, -4, -5, -6, -7, -8, -9, -10]  

In general, it doesn't cost anything to try. You can simply type this into the interpreter and see what it does.

This is all documented here as:

range(start, stop[, step]) 

but mostly I'd like to encourage you to play around and see what happens. As you can see, your intuition was spot on.

Answer 2

Yes, by defining a step:

for i in range(10, -11, -1):
    print(i)

Answer 3

In addition to the other good answers, there is an alternative:

for y in reversed(range(-10, 11)):

See the documentation for reversed().