List

L = ['Michael', 'Sarah', 'Tracy', 'Bob', 'Jack']

>>> L[:3]
['Michael', 'Sarah', 'Tracy']
>>> L[-2:]
['Bob', 'Jack']
>>> L[-2:-1]
['Bob']

>>> L = list(range(100))
>>> L
[0, 1, 2, 3, ..., 99]

>>> L[:10:2]
[0, 2, 4, 6, 8]

Tuple

>>> (0, 1, 2, 3, 4, 5)[:3]
(0, 1, 2)

String

>>> 'ABCDEFG'[:3]
'ABC'
>>> 'ABCDEFG'[::2]
'ACEG'