How to Reverse Order Using Slicing in Python

This article will demonstrate slicing in Python and the meaning of object[::-1] in slicing. Here object represents an iterable that can be sliced like a string or a list.

Slicing allows the user to access parts of a sequence like lists, tuples, and strings. Many functions can be performed using slicing, for instance, deleting items or modify items in a sequence.

First, let us understand the syntax for slicing.

1. a[start: stop] The items start from the given point and slices till stop -1.
2. a[start: ] The items start from the given point and slice till the end of an array.
3. a[: stop] The items start from the beginning and slice till stop -1.
4. a[: ] This gives the whole array as output.
5. a[start: stop: step] The items start from the given point and slices till stop -1 with provided step size.

The code below demonstrates the slicing in Python.

a = [1, 3, 5, 7, 9]
print(a[-1])
print(a[-2:])
print(a[:-2])

Output:

9
[7, 9]
[1, 3, 5]

Using a[::-1] in Python to Reverse an Object Like an Array or String

As we saw above, we have a[start: stop: step] step in slicing, and -1 means the last element of the array. Therefore, a[::-1] starts from the end till the beginning reversing the given sequence that was stored.

For example,

a = "12345"
print(a[::-1])

Output:

54321