title: Why do i get the TypeError "argument of type 'type' is not iterable"?
body: <p>I am trying to add some keys to my dictionary after testing if they are already existing keys. But I seem not to be able to do the test, every time I get the <code>TypeError "argument of type 'type' not iterable</code>.</p>
  
  <p>This is basically my code:</p>
  
  <pre><code>dictionary = dict
  sentence = "What the heck"
  for word in sentence:
        if not word in dictionary:
               dictionary.update({word:1})
  </code></pre>
  
  <p>I also tried <code>if not dictionary.has_key(word)</code> but it didn't work either so I am really confused. </p>