Valid-palindrome.py

class Solution(object):
    def isPalindrome(self, s):
        """
        :type s: str
        :rtype: bool
        """
       
        l, r = 0, len(s) - 1

        while l < r:
            if not (s[l].isalnum()):
                l += 1
                continue
            if not (s[r].isalnum()):
                r -= 1
                continue
                
            if s[l].lower() != s[r].lower():
                return False
            else:
                l += 1
                r -= 1
        return True