text: 
  # string = "aba"
  def get_none_repeat_letter_index(string):
      letterDict = {}
      for index in range(len(string)):
          if string[index] in letterDict.keys():
              letterDict.update({string[index]:letterDict[string[index]]+1})
          else:
              letterDict.update({string[index]:1})
  
      for index in range(len(string)):
          if letterDict[string[index]] is 1:
              return index
      return None
  
  def get_none_repeat_letter_index_using_split(string):
      '''
      Another method using split string.
      '''
      for index in range(len(string)):
          if string[index] not in string[index+1:]:
              return index
      return None
  
  
  def list_comprehesion(string):
      return ([index for index in range(len(string)) if string[index] not in string[index+1:]][0])
  
  
  assert get_none_repeat_letter_index("aba") == 1
  assert get_none_repeat_letter_index("abcgabc") == 3
  
  assert get_none_repeat_letter_index_using_split("aba") == 1
  assert get_none_repeat_letter_index_using_split("abcgabc") == 3
  
  assert list_comprehesion("aba") == 1
  assert list_comprehesion("abcgabc") == 3
  