title: Counting issue wth Python dictionaries
body: <p>So I'm trying to count unique letter in this function. If their are unique letters return True if there isn't return False. In the word 'Programming'
  there are two r's and two m's and two g's. Its return True where the actual answer is False? Is my logic wrong here?</p>
  
  <pre><code>def unique_chars_in_string(input_string):
      unique_chars = {}
      if input_string == "":
          return True
  
      for letter in input_string:
          if letter in unique_chars:
              unique_chars[letter]+=1
          else:
               unique_chars[letter]=1
  
  
      for k in unique_chars:
          if unique_chars[k] &gt; 1:
              return False
  
          else:
              return True
  
  
  print(unique_chars_in_string('Programming'))
  </code></pre>