Python Program to Reverse a Number

This article will disclose, Python Program to Reverse a Number using Python While Loop, Functions and Recursion.

Python Program to Reverse a Number Using While Loop

This python program allows the user to enter any positive integer and then, this program will reverse a number using Python While Loop

PYTHON CODE

# Python Program to Reverse a Number using While loop

Number = int(input("Please Enter any Number: "))
Reverse = 0
while(Number > 0):
    Reminder = Number %10
    Reverse = (Reverse *10) + Reminder
    Number = Number //10

print("\n Reverse of entered number is = %d" %Reverse)

OUTPUT

ANALYSIS:

This program allows the user to enter any positive integer and then, that number is assigned to variable Number.

Next, Condition in the While loop will make sure that, the given number is greater than 0

From the above example, User Entered value: Number = 1456 and Reverse = 0

First Iteration

Reminder = Number %10
Reminder = 1456%10 = 6

Reverse = Reverse *10+ Reminder
Reverse = 0 * 10 + 6
Reverse = 0 + 6
Reverse = 6

Number = Number //10
Number = 1456 //10
Number = 145

Second Iteration
From the first Iteration the values of both Number and Reverse has been changed as: Number = 145 and Reverse = 6

Reminder = Number % 10
Reminder = 145 % 10 = 5

Reverse = Reverse *10+ Reminder
Reverse = 6 * 10 + 5
Reverse = 60 + 5
Reverse = 65

Number = Number //10
Number = 145 //10
Number = 14

Third Iteration
From the Second Iteration the values of both Number and Reverse has been changed as: Number = 14 and Reverse = 65

Reminder = Number %10
Reminder = 14%10 = 4

Reverse = Reverse *10+ Reminder
Reverse = 65 * 10 + 4
Reverse = 650 + 4
Reverse = 654

Number = Number //10
Number = 14//10
Number = 1

Fourth Iteration
From the Second Iteration the values of both Number and Reverse has been changed as: Number = 1 and Reverse = 654

Reminder = Number %10
Reminder = 1 %10 = 1

Reverse = Reverse *10+ Reminder
Reverse = 654 * 10 + 1
Reverse = 6540 + 1
Reverse = 6541

Number = Number //10
Number = 1//10
Number = 0

Here, For the next iteration Number = 0 so, the while loop condition will fail

Python Program to Reverse a Number Using Functions

This program allows the user to enter any positive integer and then, we are going to reverse a number using Python Functions

PYTHON CODE

# Python Program to Reverse a Number using Functions

def Reverse_Integer(Number):
    Reverse = 0
    while(Number > 0):
        Reminder = Number %10
        Reverse = (Reverse *10) + Reminder
        Number = Number //10
    return Reverse

Number = int(input("Please Enter any Number: "))
Reverse = Reverse_Integer(Number)
print("\n Reverse of entered number is = %d" %Reverse)

OUTPUT

ANALYSIS:

When the compiler reaches to Reverse = Reverse_Integer (Number) line in the program then the compiler will immediately jump to below function:

def Reverse_Integer(Number):

We already explained the code LOGIC in the above example. Please refer Python Program to Reverse an Integer Using While Loop Analysis.

Last line ends with return Reverse statement.

Python Program to Reverse a Number using Recursion

This program allows the user to enter any positive integer and then, we are going to reverse a number using Python Recursion

PYTHON CODE

# Python Program to Reverse a Number using Recursion

Reverse = 0
def Reverse_Integer(Number):
    global Reverse
    if(Number > 0):
        Reminder = Number %10
        Reverse = (Reverse *10) + Reminder
        Reverse_Integer(Number //10)
    return Reverse

Number = int(input("Please Enter any Number: "))
Reverse = Reverse_Integer(Number)
print("\n Reverse of entered number is = %d" %Reverse)

OUTPUT

ANALYSIS:

When the compiler reaches to Reverse = Reverse_Integer (Number) line in the program then the compiler will immediately jump to below function:

def Reverse_Integer(Number):

In this function, below statement will help to call the function Recursively with updated value. If you miss this statement then, after completing the first line it will terminate.

Reverse_Integer(Number //10)

For example, Number = 459 will produce the output as 9

Lets see the Python If Statement,

if (Number > 0) will check whether the number is greater than 0 or not. For Recursive functions it is very important to place a condition before using the function recursively otherwise, we will end up in infinite execution (Same like infinite Loop).

Please be careful 🙂

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