First Unique Character in a String Leetcode Solution Python

Leetcode Question

Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1.

Solution (Python)

class Solution:
    def firstUniqChar(self, s: str) -> int:
        chardict = {}
        for i in range(0,len(s)):
            #print(s[i])
            if s[i] in chardict:
                value = chardict[s[i]][0]
                index = chardict[s[i]][1]
                chardict.update({s[i]:[value+1,index]})
            else:
                chardict.update({s[i]:[1,i]})
        #print(chardict)
        ans = len(s)
        for key,value in chardict.items():
            if value[0]==1 and value[1]<ans:
                ans = value[1]
        if ans!=len(s):
            return ans
        return -1