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Python Program to Check Whether a String is Palindrome or Not

In this program. you’ll learn to check whether a string is palindrome or Not

To understand this example, you should have the knowledge of following Python programming topics:

  • Python if…else Statement
  • Python Strings
  • Python String Methods

A palindrome is a string which is same read forward or backwards.

For example: "dad" is the same in forward or reverse direction. Another example is "aibohphobia" which literally means, an irritable fear of palindromes.

Source Code

# Program to check if a string
# is palindrome or not
# change this value for a different output
my_str = 'aIbohPhoBiA'
# make it suitable for caseless comparison
my_str = my_str.casefold()
# reverse the string
rev_str = reversed(my_str)
# check if the string is equal to its reverse
if list(my_str) == list(rev_str): print("It is palindrome")
else: print("It is not palindrome")

Output

It is palindrome

Note: To test the program, change the value of my_str in the program.

In this program, we have taken a string stored in my_str.

Using the method casefold() we make it suitable for caseless comparisons. Basically, this method returns a lowercased version of the string.

We reverse the string using the built-in function reversed(). Since this function returns a reversed object, we use the list() function to convert them into a list before comparing.

Check out these related Python examples:

  • Sort Words in Alphabetic Order
  • Remove Punctuations From a String
  • Count the Number of Each Vowel
  • Check Armstrong Number
  • Convert Decimal to Binary Using Recursion
  • Check Prime Number
  • Display Powers of 2 Using Anonymous Function
  • Print the Fibonacci sequence

Python Examples

Add Two Matrices
Transpose a Matrix
Multiply Two Matrices
Check Whether a String is Palindrome or Not
Remove Punctuations From a String
Sort Words in Alphabetic Order
Illustrate Different Set Operations

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Python program to check if a string is palindrome or not

Given a string, write a python function to check if it is palindrome or not. A string is said to be palindrome if reverse of the string is same as string. For example, “radar” is palindrome, but “radix” is not palindrome.

Examples:

Input : malayalam
Output : Yes
Input : geeks
Output : No

Recommended: Please try your approach on IDE first, before moving on to the solution.

1) Find reverse of string
2) Check if reverse and original are same or not.

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code

# function which return reverse of a string
def reverse(s):
    return s[::-1]
  
def isPalindrome(s):
    # Calling reverse function
    rev = reverse(s)
  
    # Checking if both string are equal or not
    if (s == rev):
        return True
    return False
  
  
# Driver code
s = "malayalam"
ans = isPalindrome(s)
  
if ans == 1:
    print("Yes")
else:
    print("No")

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Output :

Yes

Iterative Method: This method is contributed by Shariq Raza. Run loop from starting to length/2 and check first character to last character of string and second to second last one and so on …. If any character mismatches, the string wouldn’t be palindrome.

Below is the implementation of above approach:

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code

# function to check string is 
# palindrome or not 
def isPalindrome(str):
  
    # Run loop from 0 to len/2 
    for i in xrange(0, len(str)/2): 
        if str[i] != str[len(str)-i-1]:
            return False
    return True
  
# main function
s = "malayalam"
ans = isPalindrome(s)
  
if (ans):
    print("Yes")
else:
    print("No")

chevron_right

Output:

Yes

Method using inbuilt function to reverse a string: This method is contributed by Shariq Raza. In this method, predefined function ‘ ‘.join(reversed(string)) is used to reverse string.

Below is the implementation of the above approach:

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edit
close

play_arrow

link
brightness_4
code

# function to check string is 
# palindrome or not
def isPalindrome(s):
      
    # Using predefined function to 
    # reverse to string print(s)
    rev = ''.join(reversed(s))
  
    # Checking if both string are 
    # equal or not
    if (s == rev):
        return True
    return False
  
# main function
s = "malayalam"
ans = isPalindrome(s)
  
if (ans):
    print("Yes")
else:
    print("No")

chevron_right

Output:

Yes

This article is contributed by Sahil Rajput . If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to [email protected] See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

My Personal Notes
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