code: def first_unique_char(s):
      
      if (len(s) == 1):
          return 0
      ban = []
      for i in range(len(s)):
          if all(s[i] != s[k] for k in range(i + 1, len(s))) == True and s[i] not in ban:
              return i
          else:
              ban.append(s[i])
      return -1
docs: :type s: str
      :rtype: int