unique characters in a string python code example

Example 1: count characters in string python

>>> sentence = 'Mary had a little lamb'
>>> sentence.count('a')
4

Example 2: find unique char in string python

In [1]: list(set('aaabcabccd'))
Out[1]: ['a', 'c', 'b', 'd']

Example 3: first unique character in a string python

class Solution(object):
   def firstUniqChar(self, s):
      """
      :type s: str
      :rtype: int
      """
      frequency = {}
      for i in s:
         if i not in frequency:
            frequency[i] = 1
         else:
            frequency[i] +=1
      for i in range(len(s)):
         if frequency[s[i]] == 1:
            return i
      return -1
ob1 = Solution()
print(ob1.firstUniqChar("people"))
print(ob1.firstUniqChar("abaabba"))