longest palindrome

 1class Solution(object):
 2    def longestPalindrome(self, s):
 3        def helper(l, r):
 4            while 0 <= l and r < len(s) and s[l] == s[r]:
 5                l, r = l - 1, r + 1
 6            return s[l + 1: r]
 7
 8        res = ""
 9        for i in range(len(s)):
10            res = max(helper(i, i), helper(i, i + 1), res, key=len)
11        return res
12
13
14Solution().longestPalindrome("kjhdkfjhkjhaskjdhfakjshdfkjashdfkjhabcdcba")