Check if a string is palindrome using Python

A palindrome is a word, number or a phrase which is same when read from left to right or right to left.

Examples:
Rotor, Ava, Salas
top spot

1001, 12321, 111

In this topic, we will write some sample code snippets to check if a given string is palindrome.
We can do this check in multiple ways. Here we will consider the two simplest options.

By comparing each character

First we need to find the half length of the string. If the length of the string is an odd number, we can skip the middle character. Then using a for loop, compare first and last characters of the string.

For each increment, next character from start and previous character from end is compared. If all the comparisons matches, string is a palindrome, otherwise not.

def checkPalindrome(strtoCheck):
    str1 = strtoCheck.lower().replace(" ", "")    
    halfLen = len(str1)// 2

    isPalindrome = True
    #Check if character matches. From start and end position
    for i in range(halfLen):
        if(str1[i] != str1[(len(str1)-1) - i]):
            isPalindrome = False
            break
    
    if(isPalindrome == True):
        print("'" + strtoCheck + "' is a palindrome")
    else:
        print("'" + strtoCheck + "' is not a palindrome")


checkPalindrome('Rotor')
checkPalindrome('Test tset')
checkPalindrome('Test')

Output: 'Rotor' is a palindrome 'Test tset' is a palindrome 'Test' is not a palindrome

By splitting the string by half and compare

Here we don't have to use a loop to do the check. Find the half length of the string and split it into two. If the length of the string is an odd number, we can skip the middle character.

Then reverse the second half string and do a comparison. If both are equal, given string is a palindrome.

def checkPalindrome(strtoCheck):
    str1 = strtoCheck.lower().replace(" ", "")
    
    halfLen = len(str1)// 2

    firsthalf = ''
    secondhalf = ''
    if(len(str1) % 2 == 0):#Even
        firsthalf = str1[:halfLen]
        secondhalf = str1[halfLen:]
    else:#Odd
        firsthalf = str1[:halfLen]
        secondhalf = str1[halfLen+1:]
    
    #Compare frst half of the string with reversed second half
    if(firsthalf == secondhalf[::-1]):
        print("'" + strtoCheck + "' is a palindrome")
    else:
        print("'" + strtoCheck + "' is not a palindrome")


checkPalindrome('Salas')
checkPalindrome('Test')

Output: 'Salas' is a palindrome 'Test' is not a palindrome