class Solution(object):

     def isPalindrome(self, s):

         """

         :type s: str

         :rtype: bool

         """

         j = len(s) - 1

         i = 0

         flag = True

         while i != j and flag == True:

             if s[i].isalnum() and s[j].isalnum():

                 if s[i].lower() == s[j].lower():

                     flag = True

                 else:

                     flag = False

             if not s[i].isalnum() :

                 i += 1

             if not s[j].isalnum():

                 j -= 1

         return flag
             

 class Solution(object):

     def isPalindrome(self, s):

         """

         :type s: str

         :rtype: bool

         """

         j = len(s) - 1

         i = 0

         flag = True

         while i < j :

             if not s[i].isalnum() :

                 i += 1

                 continue

             if not s[j].isalnum():

                 j -= 1

                 continue

             if s[i].lower() != s[j].lower():

                     return False

             i += 1

             j -= 1

         return flag

 class Solution(object):

     def isPalindrome(self, s):

         """

         :type s: str

         :rtype: bool

         """

         new_s = "".join([i for i in s if i.isalnum() or i.isalpha()]).lower()

         return new_s == new_s[::-1]

 class Solution(object):

     def isPalindrome(self, s):

         """

         :type s: str

         :rtype: bool

         """

         import re

         s = re.sub('[^a-z0-9]','',s.lower())

         return s == s[::-1]