title: What makes sets faster than lists?
body: <p>The python wiki says: "Membership testing with sets and dictionaries is much faster, O(1), than searching sequences, O(n). When testing "a in b", b should be a set or dictionary instead of a list or tuple."</p>
  
  <p>I've been using sets in place of lists whenever speed is important in my code, but lately I've been wondering why sets are so much faster than lists. Could anyone explain, or point me to a source that would explain, what exactly is going on behind the scenes in python to make sets faster?</p>