How to inverse a List?

Question

In List slices we can print out from which index to which index with X steps.
When we use [first_index:second_index:-num] it is not working and retrieve None.
my question is how we can inverse a range of indices in a list from first_index to last_index by a negative number step.

for instance:
sqs=[0,3,5,30,13,15,36,1,12,9,24]
print(sqs[2:8:-2])
my desired output (in a single command):
[1,15,30]

any idea?
Thanks in advance.

Answer 1

As for your code, if you start at 2 and move backwards, you will never reach 8 - that's why you get an empty list (it's not None, it's an empty list!):

>>> sqs=[0,3,5,30,13,15,36,1,12,9,24]
>>> print(sqs[2:8:-2])
[]

Try this:

>>> print(sqs[7:2:-2])
[1, 15, 30]

Answer 2

sqs[::-1] should reverse the list. is this what you mean by inverse a list? I've seen inverse on matrices and numbers. first time seeing inverse on a list.

Answer 3

Thanks Bogdan Sass
It was what I exactly wanted but i didn't try it.
Thanks again.

Warm regards.

Answer 4

print(sq[::-1]) it will inverse the list with square of the number !!