Palindrome in Python: How to Check a Number or String is Palindrome?

when checking for if a number is Palindrome or not with Python, we will be using while loop and in-built functions. For beginners, Edureka has a 360° Python course page  which will help you learn Python from scratch even if you don’t have much coding knowledge.

What is a Palindrome?

A palindrome is nothing but any number or a string which remains unaltered when reversed.

Example: 12321
Output: Yes, a Palindrome number

Example: RACECAR
Output: Yes, a Palindrome string

It is evident that letters form mirror images on reversal.

Now that you understood the concept, let’s simply dive into a program to check palindrome in Python.

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Palindrome Algorithm

Let’s see how we check for Palindromes in Python

To check a Palindrome in Python, the program should check whether a given string is the same when read forwards and backward.

Consider the following Python program

string = input(“Enter a string: ”)
if string == string[::-1]:
print(“The string is a palindrome”)
else:
print(“Not a palindrome”)

First, it asks the user to enter a string and stores it.

Then, it checks if the string is same as its reverse.

If it’s equal to its reverse, the program prints “The string is a palindrome.”

Otherwise, it prints “The string is not a palindrome.”

Palindrome Program using Native Approach

The native approach is one of the easiest way to check the Palindrome in Python. Let’s jump onto an example to check whether a given input string is palindrome or not.

string = input(“Enter a string: ”)
if string == string[::-1]:
print(“The string is a palindrome”)
else:
print(“Not a palindrome”)

Enter a string: level
Output: The string is a palindrome

Moving ahead in Python palindrome program examples, let’s see how to check a string whether it’s a palindrome using the Iterative method.

Palindrome Program using Iterative Method

String = input(“Enter a string: ”)
is_palindrome = True
for i in range (0, int (len(string) / 2)):
if string[i] != string[len(string) - i - 1]:
is_palindrome = False
break
if is_palindrome:
print(“The string is palindrome”)
else:
print(“Not a palindrome”)

Enter a string: 1221
Output: The string is a palindrome

Now, let’s see how to check a string whether it’s a palindrome using While loop.

Palindrome Program using While Loop

This is one of the easiest programs to find Palindrome program using while loop in Python Programming. Let’ dive into an example to check whether a given input is a palindrome or not.

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

Output:

Enter a number:121
The number is palindrome!

Moving ahead in Python palindrome program examples, let’s us see how to check a string whether its a palindrome or not using built-in functions.

Palindrome Program( String) using inbuilt Method

string=input(("Enter a string:"))
if(string==string[::-1]):
      print("The string is a palindrome")
else:
      print("Not a palindrome")

Output:

Explanation: In the above program, first take input from the user (using input OR raw_input() method) to check for palindrome. Then using slice operation [start:end:step], check whether the string is reversed or not. Here, step value of -1 reverses a string. If yes, it prints a palindrome else, not a palindrome.

Moving ahead, let’s see how to check a string whether it’s a palindrome using inbuilt functions to reverse a string.

Palindrome Program using Inbuilt Method

string = input("Enter a string: ")
reversed = ''.join(reversed(string))
if string == reversed:
print("The string is a palindrome")
else:
print("Not a palindrome")
Enter a string: 1212

Output: Not a palindrome

Now, it’s time to see how to check a string whether it’s a palindrome using One Extra Variable.

Palindrome Program using One Extra Variable

string = input("Enter a string: ")
w = ""
for i in string:
w = i + w
if string == w:
print("The string is a palindrome")
else:
print("Not a palindrome")
Enter a string: civic

Output: The string is a palindrome

Let’s see how to check a string whether it’s a palindrome using flag.

Check if a String is Palindrome or not using flag

string = input("Enter a string: ")
index_backwards = -1
is_not_palindrome = 0
for index_forward in range(len(string)):
if string[index_forward] != string[index_backwards]:
is_not_palindrome = 1
break
index_backwards -= 1
if is_not_palindrome == 1:
print("The string is a palindrome")
else:
print("Not a palindrome")

Enter a string: 2003
Output: Not a palindrome

Moving ahead, we’ll see how to check a string whether it’s a palindrome using recursion.

Check if a String is Palindrome or not using recursion

string = input("Enter a string: ")
string = string.lower()
l = len(string)
is_palindrome = True
while l > 1:
if string[0] == string[-1]:
string = string[1:-1]
l = len(string)
else:
is_palindrome = False
break
if is_palindrome:
print("The string is a palindrome")
else:
print("Not a palindrome")

Enter a string: rotor
Output: The string is a palindrome

FAQs

• What is an example of a palindrome in Python?

A palindrome is a sequence of characters which reads the same backward as forward

In Python, we can create a simple program to check if it’s a palindrome.

string = input(“Enter a word: ”)
if string == string[::-1]:
print(“The string is a palindrome”)
else:
print(“Not a palindrome”)
In this example, the word "radar" is a palindrome.

• How do you find the palindrome between two numbers in Python?

To find the palindrome numbers between two numbers, we can write a loop to check each number in the range and see if it reads the same forward and backward.

Here’s a simple example

start = 100
end = 200
palindromes = []
for number in range(start, end + 1):
if str(number) == str(number)[::-1]:</span>
palindromes.append(number)
print("Palindromes: ",palindromes)

1. We start at 100 (start = 100).
2. We end at 200 (end = 200).
3. We create an empty list called palindromes.
4. We loop over each number.
5. If it’s a palindrome, we add it to the list.
6. We print the list.

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