What is palindrome integer in python?

This is a Python Program to check whether a given number is a palindrome.

Problem Description

The program takes a number and checks whether it is a palindrome or not.

Problem Solution

1. Take the value of the integer and store in a variable.
2. Transfer the value of the integer into another temporary variable.
3. Using a while loop, get each digit of the number and store the reversed number in another variable.
4. Check if the reverse of the number is equal to the one in the temporary variable.
5. Print the final result.
6. Exit.

Program/Source Code

Here is source code of the Python Program to check whether a given number is a palindrome. The program output is also shown below.

 
n=int(input("Enter number:"))
temp=n
rev=0
while(n>0):
    dig=n%10
    rev=rev*10+dig
    n=n//10
if(temp==rev):
    print("The number is a palindrome!")
else:
    print("The number isn't a palindrome!")

Program Explanation

1. User must first enter the value of the integer and store it in a variable.
2. The value of the integer is then stored in another temporary variable.
3. The while loop is used and the last digit of the number is obtained by using the modulus operator.
4. The last digit is then stored at the one’s place, second last at the ten’s place and so on.
5. The last digit is then removed by truly dividing the number with 10.
6. This loop terminates when the value of the number is 0.
7. The reverse of the number is then compared with the integer value stored in the temporary variable.
8. If both are equal, the number is a palindrome.
9. If both aren’t equal, the number isn’t a palindrome.
10. The final result is then printed.

Runtime Test Cases

 
Case 1
Enter number:121
The number is a palindrome!
 
Case 2
Enter number:567
The number isn't a palindrome!

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Sometimes, we have an application of checking a number is palindrome or not and it’s quite common while day-day programming or competitive programming, it’s easy to reverse a number and check it but sometimes for readability and reducing lines of code, we require to perform this in one-liner logic. Let’s discuss certain ways in which this can be achieved.

Input : test_number = 12321
Output : True

Input : test_number = 1234
Output : False

Method #1 : Using math.log() + recursion + list comprehension
The combination of above three functions can perform this particular task easily, the logs function extracts the number of digits which is powered by 10 to get the number for that iteration for comparison. The process is recurred to test for palindrome.

import math

def rev(num):

    return int(num != 0) and ((num % 10) * \

             (10**int(math.log(num, 10))) + \

                          rev(num // 10))

test_number = 9669669

print ("The original number is : " + str(test_number))

res = test_number == rev(test_number)

print ("Is the number palindrome ? : " + str(res))

Output:

The original number is : 9669669
Is the number palindrome ? : True

 
Method #2 : Using str() + string slicing
This can also be done by converting the number into a string and then reversing it using the string slicing method and comparing it, truth of which returns the answer to it.

test_number = 9669669

print ("The original number is : " + str(test_number))

res = str(test_number) == str(test_number)[::-1]

print ("Is the number palindrome ? : " + str(res))

Output:

The original number is : 9669669
Is the number palindrome ? : True

We can also read input as string and then simply check for palindrome.

num = input("Enter a number")

if num == num[::-1]:

    print("Yes its a palindrome")

else:

    print("No, its not a palindrome")