Python Program to Reverse a Number

Write a program in python to reverse the digits of a number.

Example:
Input: number = 1234
Output: reverse number = 4321

Reverse a Number in Python

# Python program to reverse a number

def reverse(number):
  reverse_number = 0
  
  while(number>0):
    r = number % 10;
    reverse_number = reverse_number*10 + r
    number = number / 10
  return reverse_number;
  
  
# Driver Program

number = 1234

print("Given Number: ")
print(number)

print("Reversed Number: ")
print(reverse(number))

Output:

Given Number: 1234
Reversed Number: 4321

Explanation:

We have defined a function reverse which takes one argument number. reverse_number variable is used to hold the reverse the number, initialized to 0. Now we get the last digit of original number by using modulo operation. We use the formula reverse_number = reverse_number*10 + r where r is the remainder i.e. the last digits of original number. Then divide the original number. Continue this process until original number becomes 0.

Input: number = 1234

Pass this to reverse() function as reverse(number)

Set reverse number = 0

Get last digit r = 1234 % 10 = 4

reverse number = reverse number * 10 + r

So reverse number = 0 * 10 + 4 = 4

Divide original number by 10

number = number / 10

number = 1234 / 10 = 123

Again obtain as above, so r = 3
Again calculate reverse number as above, so 
reverse number = 4 * 10 + 3 = 43
Again divide original number by 10, so
number = 12 (after dividing)

Again find r, r = 2
calculate reverse number = 43 * 10 + 2 = 432
Divide number by 10
So number = 1

Again find r, r = 1
calculate reverse number = 432 * 10 + 1 = 4321

Divide number by 10
So number = 1 / 10 = 0
So stop here and return the reverse number


Output: reverse number = 4321
You can also do this without using function, below is the code for that
# Python program to reverse a number

# set or accept number to reverse
number = 1234

# store original number
original_number = number

reverse_number = 0
  
while(number>0):
    r = number % 10;
    reverse_number = reverse_number*10 + r
    number = number / 10

print("Given Number: ")
print(original_number)

print("Reversed Number: ")
print(reverse_number)