What is the meaning of “int(a[::-1])” in Python?

Question

Kindly help me in understanding the below code:

str(int(a[::-1]))

Answer 1

Let's take a string variable named as str1. The syntax that you are referring to is known as Slice notation in Python-

list[<start>:<stop>:<step>]

So, when you write:

[::-1]

It will begin from the end towards the first extracting each element. So it will reverse a. This is applicable for lists/tuples as well.

Say for instance:

>>> a = '1234'

>>> a[::-1]

'4321'