Longest Substring Without Repeating Characters

class Solution(object):
    def lengthOfLongestSubstring(self, s):
        """
        :type s: str
        :rtype: int
        """
        string = []
        length = 0
        max = 0
        for i in range(len(s)):
            if s[i] not in string:
                string.append(s[i])
            else:
                pos = string.index(s[i])
                if pos<len(string)-1:
                    string = string[string.index(s[i])+1:]
                else:
                    string = []
                string.append(s[i])
            if len(string)>max:
                max = len(string)
        return max