Reverse a Number in Python using Function

We will develop a program to reverse a number in python using function. To reverse a number we need to extract the last digit of the number and add that number into a temporary variable with some calculation, then remove the last digit of the number. Do these processes until the number becomes zero.

To remove the last digit the modulus operator (%) will be helpful for us, and to remove the last digit division operator (/) can be used. To add the last digit first we need to multiply the previous value by 10. Once you get the logic, you can write the program in any language.

Example of the reverse a number:-
Number: 54035
Reverse number: 53045

Procedure to find reverse of a number,

1. Take a number
2. Declare a temporary variable and initialize it with 0
3. Find the last digit of the number
4. Multiply the temporary variable by 10
5. Add that last digit to the temporary variable
6. Remove the last digit of the number.
7. Repeat this process from 3 to 6 until the number becomes 0.

Reverse a Number using Function in Python

We can take the help of a function to reverse a number in python using while loop. A function is a block of code that performs a specific task. We will take an integer number while declaring the variables. Then, call the function and finally, the result will be displayed on the screen.

# Python program to reverse a number using function

def findReverse(n):  #user-defined function
   # calculate reverse of number
   reverse = 0
   reminder = 0
   while(n != 0):
      remainder = n % 10
      reverse = reverse * 10 + remainder
      n = int(n / 10)
   return reverse

# take inputs
num = 123
# calling function and display result
reverse = findReverse(num)
print('The reverse number is =', reverse)

Output:-

The reverse number is = 321

Reverse a Number in Python using Function

In the previous program, inputs are hardcoded in the program but in this program, input will be provided by the user.

# Python program to reverse a number using function

def findReverse(n):  #user-defined function
   # calculate reverse of number
   reverse = 0
   reminder = 0
   while(n != 0):
      remainder = n % 10
      reverse = reverse * 10 + remainder
      n = int(n / 10)
   return reverse

# take inputs
num = int(input('Enter the number: '))

# calling function and display result
reverse = findReverse(num)
print('The reverse number is =', reverse)

Output for the input values test-case-1:-

Enter the number: 12345
The reverse number is = 54321

Output for the input values test-case-2:-

Enter the number: 98745
The reverse number is = 54789

Python Program to Reverse a Number using Function

In this program, we are using the for loop to reverse a number using function.

# Python program to reverse a number using function

def findReverse(n):  #user-defined function
   # calculate reverse of number
   reverse = ''
   for i in range(len(n), 0, -1):
      reverse += n[i-1]
   return reverse

# take inputs
num = input('Enter the number: ')

# calling function and display result
reverse = findReverse(num)
print('The reverse number is =', reverse)

Output:-

Enter the number: 605041
The reverse number is = 140506

reverse a number in python using recursion

We can also use the recursion technique to reverse a number in python. A technique of defining the method/function that contains a call to itself is called recursion.

# Python program to reverse a number using recursion

reverse, base = 0, 1
def findReverse(n):
    global reverse  #function definition
    global base   #function definition
    if(n > 0):
        findReverse((int)(n/10))
        reverse += (n % 10) * base
        base *= 10
    return reverse

# take inputs
num = int(input('Enter the number: '))

# calling function and display result
print('The reverse number is =', findReverse(num))

Output:-

Enter the number: 15456
The reverse number is = 65451

---

Q1) Write a program to reverse an integer value 54321 in Python.

def findReverse(n):
   # calculate reverse of number
   reverse = 0
   reminder = 0
   while(n != 0):
      remainder = n % 10
      reverse = reverse * 10 + remainder
      n = int(n / 10)
   return reverse

# take inputs
num = 12345
# calling function and display result
print('The reverse number is =', findReverse(num))

Output:-

The reverse number is = 54321

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