Checking user input string is Palindrome or not in Python

A string is said Palindrome if it is same when reversed.
Examples of Palindrome : level, racecar , radar , malayalam
Read on string reverse in Python

Checking By using reversed()

We can reverse the sequence of all the elements of any iterable object by using using reversed() function . String method join() creates a string by joining all the elements.

str='level'
str_rev=''.join(reversed(str))
if(str==str_rev):
  print("The string ",str," is a Palindrome ")
else:
  print("The string ",str," is NOT a Palindrome ")

Output

The string  level  is a Palindrome

By looping & length

By using for loop we can reverse a sting. The function len() will return the length of the string. Using the length of the string we can start from the last position char and come upto the first char.

str='plus2net'
n=len(str) # length of the string
x=''
for i in range(n-1,-1,-1):
  #print(str[i],end='')
  x=x+str[i]
if(x==str):  
  print(" \n The string ",str," is a Palindrome ")
else:
  print("\n The string ",str," is NOT a Palindrome ")

Output

The string  plus2net  is NOT a Palindrome

By using string slice

This is the shortest code to reverse a string.

str=input("Enter a string: ")
str_rev=str[::-1]
if(str_rev==str):  
  print(" \n The string ",str," is a Palindrome ")
else:
  print("\n The string ",str," is NOT a Palindrome ")

Output

Enter a string: radar
 
 The string  radar  is a Palindrome

for loop

All strings are iterable object so we can use for loop to iterate through the string.

str=input("Enter any string : ")
x=''
for i in str:
  x=i+x
if(x==str):  
  print(" \n The string ",str," is a Palindrome ")
else:
  print("\n The string ",str," is NOT a Palindrome ")

Output

Enter any string : malayalam
 
 The string  malayalam  is a Palindrome

Case insensitive

All above codes are case sensitive. By making the string to upper case ( upper() ) or by making to lower case ( lower() ) we can check for Palindrome without case sensitive.

str=input("Enter a string: ")
str1=str.upper()
str_rev=str1[::-1]
if(str_rev==str1):  
  print(" \n The string ",str," is a Palindrome ")
else:
  print("\n The string ",str," is NOT a Palindrome ")

Output

Enter a string: Radar
 
 The string  Radar  is a Palindrome

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Palindrome in Python

Checking By using reversed()

By looping & length

By using string slice

for loop

Case insensitive

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