LongestSubstring without repeating characters

solution.py

class Solution(object):
    def lengthOfLongestSubstring(self, s):
        if not s or len(s) == 0: return 0
        store = {}
        max_len, prevIdx, idx, currChar = 0, 0, 0, ''
        while idx < len(s):
            currChar = s[idx]
            if currChar not in store:
                store[currChar] = idx
            else:
                curr_len = idx-prevIdx
                max_len = max(max_len, curr_len)
                currIdx = store[currChar]
                prevIdx = max(prevIdx, currIdx+1)
                store[currChar] = idx
            idx += 1
        max_len = max(max_len, idx-prevIdx)
        return max_len