I don't know what s[::-1] is in Python [duplicate]

Answer 1

It reverses a sequence using slicing.

>>> s = 'hello'
>>> s[::-1]
'olleh'

The slice notation [] is a way to get a subset of some iterable container. It has the syntax

[start : stop : step]

See this post for more details.

Answer 2

Slicing is an operation that gives you some elements out of a sequence.

s[a:b:c] means "the items starting at a, stopping at b, with a step of c".

If you have s[::-1] that means "the whole sequence, going backwards".