[Start:Stop:Step]

>>> my_list = list(range(20))
>>> my_list 
[0,1,2,3, ... , 19]
>>> my_list[::2]
[0,2,4,6,8, ... ,18]
>>> my_list[2::2]
[2,4,6,8, ... ,18]

with Strings too

>>> "Oklahoma"[::2]
'Olhm'
>>> "Oklahoma"[::-1]
'amohalkO'

Backwards

>>> my_list[::-2]
[19,17,15,13, ... , 3, 1]
>>> my_list[2:8:-1]
[]                  # Logically, you cannot get to 8 counting from 2 backwards!
>>> my_list[8:2:-1] # This is the right way to do it.
[8,7,6,5,4,3]
>>> my_list[7-1]
[7,6,5,4,3,2]
>>> my_list[-2]
18

Delete & Replace Slices

>>> my_list = [1,2,'a','b','c','d',5,6,7,'f','g','h',8,9,'j']

Using del

>>> del my_list[:2]
>>> my_list
['a','b','c','d',5,6,7,'f','g','h',8,9,'j']

Replace Slice with a Slice

>>> my_list[4:7] = ['e','f']
>>> my_list
['a','b','c','d','e','f','f','g','h',8,9,'j']
>>> my_list.remove('f')
['a','b','c','d','e','f','g','h',8,9,'j']

Replace Slice with an item

>>> my_list[8:10] = ['i']
>>> my_list
['a','b','c','d','e','f','g','h','i','j']