title: unique elements in two lists
body: <p>I was thinking if it's possible to create a list of unique elements from two lists shorter but without using <code>set</code>?</p>
  
  <pre><code>l1 = [1,1,2,2,3]
  l2 = [2,1,3,3,4]
  unique = []
  for elem in l1+l2:
      if elem not in unique:
          unique.append(elem)
  print unique
  
  [1,2,3,4]
  </code></pre>
  
  <p>Thanks for your ideas</p>