387. First Unique Character in a String

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.

Examples:

s = "leetcode"return 0.s = "loveleetcode",return 2.

Note: You may assume the string contain only lowercase letters.

class Solution(object):
    def firstUniqChar(self, s):
        """
        :type s: str
        :rtype: int
        """
        letters={}
        for c in s:
            letters[c]=letters.get(c,0)+1
        for c in s:
            if letters[c] is 1:
                return s.index(c)
        return -1