Python program to reverse a number

In this post, you will learn how to write Python program to reverse a number. Such a type of question can improve your logical problem solving skill.

Python program to reverse a number using while loop

In the given Python program, we have asked the user to enter an integer number. The while loop is used and the last digit of the number is obtained by using the modulus operator. Then, the last digit is stored at the one's place, second last at the ten's place and so on. The last digit is then removed by truly dividing the number with 10. This loop terminates when the value of the number is 0. Then, the reverse of the number is printed.

# user input 
num = int(input("Enter the number: "))  
  
# Initiate value to null  
rev_num = 0  
  
# reverse the integer number using the while loop  
  
while (num > 0):  
    remainder = num % 10  
    rev_num = (rev_num * 10) + remainder  
    num = num // 10  
  
# Display the result  
print("The reverse number : {}".format(rev_num))

Output of the above code:

Enter the number: 98235781
The reverse number : 18753289

Python program to reverse a number using for loop

Here, we have used the for loop to reverse a number using Python programming language.

# Python program to reverse a number 
# using for loop

# user input 
num = input("Enter the number: ") 

# calculating reverse of number
reverse = ''
for i in range(len(num), 0, -1):
   reverse += num[i-1]

# print reverse of number
print('Reverse number: ', reverse)

Output of the number:

Enter the number: 
987645
Reverse number:  546789

Python program to reverse a number using recursion

Recursion function is a function which is call itself. In the given example, we call the recursion function to get the reverse of a number. A recursion function continues until some condition is met to prevent it. That's why, we use the if statement to break the infinite recursion. In the given Python program, we have used recursion to reverse a given number -

num = int(input("Enter the number: "))  
rev_num = 0  
def reverse_num(num):  
    global rev_num   
    if (num > 0):  
        Reminder = num % 10  
        rev_num = (rev_num * 10) + Reminder  
        reverse_num(num // 10)  
    return rev_num
  
rev_num = reverse_num(num)  
print("Reverse of entered number: %d" % rev_num)

Output of the above code:

Enter the number: 98765421
Reverse of entered number: 12456789

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