Python program to check whether the string is Symmetrical or Palindrome

When it is required to check if a string is symmetrical or it is a palindrome, a method can be defined, that uses the ‘while’ condition. Another method is defined to check the symmetry that uses the ‘while’ and ‘if’ conditions too.

A palindrome is a number or string, which when read from left to right or right to left is the same value. The index values are the same.

Example

Below is a demonstration for the same −

def check_palindrome(my_str):
   mid_val = (len(my_str)-1)//2
   start = 0
   end = len(my_str)-1
   flag = 0
   while(start<mid_val):
   if (my_str[start]== my_str[end]):
      start += 1
      end -= 1
   else:
      flag = 1
      break;
   if flag == 0:
      print("The entered string is palindrome")
   else:
      print("The entered string is not palindrome")
def check_symmetry(my_str):
   n = len(my_str)
   flag = 0
   if n%2:
      mid_val = n//2 +1
   else:
      mid_val = n//2
   start_1 = 0
   start_2 = mid_val
   while(start_1 < mid_val and start_2 < n):
      if (my_str[start_1]== my_str[start_2]):
         start_1 = start_1 + 1
         start_2 = start_2 + 1
      else:
         flag = 1
         break
   if flag == 0:
      print("The entered string is symmetrical")
   else:
      print("The entered string is not symmetrical")
my_string = 'phphhphp'
print("The method to check a palindrome is being called...")
check_palindrome(my_string)
print("The method to check symmetry is being called...")
check_symmetry(my_string)

Output

The method to check a palindrome is being called...
The entered string is palindrome
The method to check symmetry is being called...
The entered string is not symmetrical

Explanation

• A method named ‘check_palindrome‘ is defined, that takes a string as a parameter.
• The middle value is calculated by doing floor division with 2.
• The start value is assigned to 0, and end value is assigned to the last element.
• A variable named flag is assigned to 0.
• A while condition begins, and if the start and end elements are equal, the start value is incremented, and end value is decremented.
• Otherwise, the flag variable is assigned to 1, and it breaks out of the loop.
• If the value of flag is 0, the string would be a palindrome, otherwise not.
• Another method named ‘check_symmetry’ is defined, that takes a string as a parameter.
• The length of the string is assigned to a variable.
• If the remainder of the length and 2 is not 0, the middle value is changed.
• The start and middle value are changed again.
• Another ‘while’ condition is used, and the start values are changed again.
• If the value of flag is 0, then the string is considered symmetrical.
• Otherwise not.