Leetcode:Reverse Integer Python Solution

The question:
Given a 32-bit signed integer, reverse digits of an integer.

Example 1:Input: 123Output: 321Example 2:Input: -123Output: -321Example 3:Input: 120Output: 21

Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231, 231 − 1]