a=[1,2,3,4,5,6]
> a[:1] # stop at index 1
[1]
>a[:2] # stop at index 2
[1, 2]
>a[:-2] # stop at index -2
[1, 2, 3, 4]
>a[1:1] # start at 1 and stop at index 1
[]
>a[1:4] # start at 1 and stop at index 4
[2, 3, 4]
> a[-5:-1] # start at -5 and stop at index -1
[2, 3, 4, 5]