title: TypeError 'set' object does not support item assignment
body: <p>I need to know why it won't let me increase the value of the assignment by 1:</p>
  
  <pre><code>keywords = {'states' : 0, 'observations' : 1, 'transition_probability' : 2, 'emission_probability' : 3}
  keylines = {-1,-1,-1,-1}
  
  lines = file.readlines()
  for i in range(0,len(lines)):
      line = lines[i].rstrip()
      if line in keywords.keys():
          keylines[keywords[line]] = i + 1 &lt;&lt; this is where it is giving me the error
  </code></pre>
  
  <p>I ran it as a class and it worked fine, but now as an in-line code piece it gives me this error.</p>