Reverse a Number in Python

July 29, 2023

Reverse a number in python programming

Find the Reverse of a Number in Python

Given an integer input the objective is to reverse the given integer number using loops and slicing. Therefore, we’ll write a program to Find the Reverse of a Number in Python Language.

Example
Input : 123
Output : 321

Find the Reverse of a Number in Python Language

We need to write a python code to reverse the given integer and print the integer. The typical method is to use modulo and divide operators to break down the number and reassemble again in the reverse order. Here are some of the methods to solve the above mentioned problems,

  • Method 1: Using Simple Iteration
  • Method 2: Using String Slicing
  • Method 3: Using Recursion

Let’s go through the above mentioned methods in the sections below.

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Method 1: Using Simple Iteration

Working

In this method we’ll use the concept of loops to repeat the process of breaking down the number and adding it back in the reverse order.

For a given integer variable number we perform the following,

  • Run a while loop with the condition number >0.
    • Extract the last digit as Remainder using Modulo operator.
    • Using the formula reverse = ( reverse * 10 ) + remainder , we keep changing the reverse value.
    • Break down the Nunber using divide operator.
  • Print the reverse variable.

Let’s implement the above mentioned Logic in Python Language.

Python Code

Run 
num = 1234
temp = num
reverse = 0
while num > 0:
    remainder = num % 10
    reverse = (reverse * 10) + remainder
    num = num // 10

print(reverse)

Output

4321

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Method 2: Using String Slicing

Working

In this method we’ll use the string slicing methods to reverse the number. First we’ll convert the number into a string and then using the string slicing property in python language, we’ll slice the string to break it down and add it up in reverse order.

For a given integer input, we perform the following operations,

  • Convert the number into string format.
  • Reverse the number using string slicing.

Let’s implement the above mentioned logic in Python Language.

Python Code

Run 
num = 1234
print(str(num)[::-1])

Output

4321

Method 3: Using Recursion

Working

In this method we’ll use recursion to perform all the operations we perform in method 1. We’ll use the same formula but instead of iterating through a loop, we’ll use recursion. To know more about recursion, check out our page Recursion in Python.

Given an integer input number, we perform the following,

  • Define a recursive function recursum() that takes in number and reverse variable as arguments.
  • Set the base case as number == 0 and step recursive call as recursum(num/10, reverse).
  • Print the returned value using print() function.

Let’s implement the above mentioned logic in Python Language.

Python Code

Run 
def recursum(number,reverse):
  if number==0:
    return reverse
  remainder = int(number%10)
  reverse = (reverse*10)+remainder
  return recursum(int(number/10),reverse)

num = 1234
reverse = 0
print(recursum(num,reverse))

Output

4321

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43 comments on “Reverse a Number in Python”


  • Harsh

    num = [str(d) for d in input(“Enter the Number:”)]
    s=int(”.join(num[::-1]))
    print(‘Reverse order is:’,s)


  • himanshu

    Correct one……
    num = (input(“Enter the number: “))
    for i in str(num[::-1]):
    print(i, end=””)


  • himanshu

    num = (input(“Enter the number: “))
    lst = []
    for i in str(num[::-1]):
    lst.append(i)
    print(i, end=””)


  • GS

    we can also implement this using list ,list version is very short ?
    li=list(input(“Enter the No.”))
    print(“Reverse of this no. is “,””.join(li[::-1]))


    • HelpPrepInsta

      thanks Ashish, we’ll surely consider this approach. Or if you want you can also comment the code, and we will post it on this page


      • GS

        so this my approach for reversing the list

        #taking input and converting it as list

        li=list(input(“Enter the No.”))

        #now using string join method we can join the list and this code li[::-1] will reverse the list this method is called reversing list by slicing method

        print(“Reverse of this no. is: ” , “”.join(li[::-1]))


    • Care

      We have used temp here, for creating a copy of the user inputed number, so that in the end we can print both the original number and the reversed number

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