 <p>You can use sets.</p> <p>Example:</p> <pre><code>&gt;&gt;&gt; list1 = ['a', 'b', 'c'] &gt;&gt;&gt; list2 = ['c', 'd', 'e'] &gt;&gt;&gt; set(list1) - set(list2) {'b', 'a'} </code></pre> <p>Sets by default do not preserve order. If order is important for you, check the recipe for <a href="http://code.activestate.com/recipes/576694-orderedset/" rel="nofollow"><code>OrderedSet</code></a>.</p>