title: How to efficiently compare two unordered lists (not sets)?
body: <pre><code>a = [1, 2, 3, 1, 2, 3]
  b = [3, 2, 1, 3, 2, 1]
  </code></pre>
  
  <p>a &amp; b should be considered equal, because they have exactly the same elements, only in different order.</p>
  
  <p>The thing is, my actual lists will consist of objects (my class instances), not integers.</p>