125. 验证回文串

https://leetcode-cn.com/problems/valid-palindrome/comments/

class Solution:
    def isPalindrome(self, s):
        """
        :type s: str
        :rtype: bool
        """
        #将s过滤，只保留数字和字母，再转为小写
        s = ''.join(filter(str.isalnum, s)).lower()
        #检查对称
        return s == s[::-1]