title: Comparing list item values to other items in other list in Python
body: <p>I want to compare the values in one list to the values in a second list and return all those that are in the first list but not in the second i.e.</p>
  
  <pre><code>list1 = ['one','two','three','four','five']
  list2 = ['one','two','four']
  </code></pre>
  
  <p>would return 'three' and 'five'.</p>
  
  <p>I have only a little experience with python, so this may turn out to be a ridiculous and stupid way to attempt to solve it, but this what I have done so far:</p>
  
  <pre><code>def unusedCategories(self):
      unused = []
      for category in self.catList:
          if category != used in self.usedList:
              unused.append(category)
      return unused
  </code></pre>
  
  <p>However this throws an error 'iteration over non-sequence', which I gather to mean that one or both 'lists' aren't actually lists (the raw output for both is in the same format as my first example)</p>