title: Python - removing items from lists
body: <pre><code># I have 3 lists:
  L1 = [1, 2, 3, 4, 5, 6, 7, 8, 9]
  L2 = [4, 7, 8]
  L3 = [5, 2, 9]
  # I want to create another that is L1 minus L2's memebers and L3's memebers, so:
  L4 = (L1 - L2) - L3  # Of course this isn't going to work
  </code></pre>
  
  <p>I'm wondering, what is the "correct" way to do this. I can do it many different ways, but Python's style guide says there should be only 1 correct way of doing each thing. I've never known what this was.</p>