title: python simpler way to find missing items in a list in relation to another list
body: <p>I was struggling to properly title this question but I will try and explain this situation.</p>
  
  <p>I have two lists</p>
  
  <pre><code>l1=['beststreet', 'borocd', 'am_linkid3', 'bestfrom', 'resurf19', 'rmmweekly']
  l2=['beststreet', 'borocd', 'bestfrom', 'rmmweekly','weird','noises']
  </code></pre>
  
  <p>l1 will always remain the same. </p>
  
  <p>l2 can either contain the exact items as l1 or have only some of the items as l1 and in any scenario there can be extra items in the list. </p>
  
  <p>GOAL: find only the missing items in l2 that are in l1 (disregard the extra items in l2)</p>
  
  <p>here is my full code for this, it works totally fine I just feel like I am overthinking this and what I want can have a simpler more pythonic workflow</p>
  
  <pre><code>l1=['beststreet', 'borocd', 'am_linkid3', 'bestfrom', 'resurf19', 'rmmweekly']
  l2=['beststreet', 'borocd', 'bestfrom', 'rmmweekly','weird','noises']
  
  result = [[n if n in l1 else None, n if n in l2 else None] for n in set(l1 + l2)]
  
  missing_columns=[]
  for r in result:
      if None in r:
          exists= [z for z in l1 if z in r]
          if exists:
              missing_columns.append(exists[0])
  print missing_columns
  </code></pre>