Python Program to Reverse a Number using While Loop

1. Introduction

In this tutorial, we will learn how to write a Python program to reverse a number.

Reversing a number is a common task in programming that can be required in various applications such as algorithms, palindromes, or simply formatting. Python provides multiple ways to reverse a number, and in this blog post, we'll focus on a simple and efficient method to achieve this.

Reversing a number means reordering its digits in the opposite direction. For example, if we reverse the number 12345, the output should be 54321. This process involves taking each digit from the original number, starting from the end, and appending it to a new number.

2. Program Steps

1. Accept or define the number to be reversed.

2. Initialize a variable to store the reversed number.

3. Extract each digit from the original number and add it to the reversed number.

4. Update the original number by removing the extracted digit.

5. Repeat steps 3 and 4 until the original number is reduced to zero.

6. Output the reversed number.

3. Code Program

# Function to reverse a number
def reverse_number(n):
    # Initialize the reversed number to 0
    reversed_num = 0
    # Loop until the number is greater than 0
    while n > 0:
        # Get the last digit of the number
        digit = n % 10
        # Add the digit to the reversed number's correct place
        reversed_num = reversed_num * 10 + digit
        # Remove the last digit from the number
        n = n // 10
    # Return the reversed number
    return reversed_num

# Number to be reversed
number = 12345
# Call the function and print the result
print(reverse_number(number))

Output:

54321

Explanation:

1. The function reverse_number is defined to take an integer n.

2. reversed_num is initialized to 0 and will be used to construct the reversed number.

3. A while loop continues to run as long as n is greater than 0.

4. Inside the loop, digit extracts the last digit of n using the modulus operator n % 10.

5. reversed_num is updated by multiplying it by 10 (to shift digits to the left) and adding digit to it.

6. n is updated by performing integer division by 10, effectively removing the last digit from n.

7. Once n is reduced to 0, the loop ends, and reversed_num is returned.

8. The function is then called with number as the argument, and the result is printed, showing 54321, the reverse of 12345.