Syntax error Python program to check whether the string is Symmetrical or Palindrome

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 −

 Live Demo

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.
Updated on: 2021-03-12T13:09:01+05:30

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