title: Checking if all elements in a list are unique
body: <p>What is the best way (best as in the conventional way) of checking whether all elements in a list are unique?</p>
  
  <p>My current approach using a <code>Counter</code> is:</p>
  
  <pre><code>&gt;&gt;&gt; x = [1, 1, 1, 2, 3, 4, 5, 6, 2]
  &gt;&gt;&gt; counter = Counter(x)
  &gt;&gt;&gt; for values in counter.itervalues():
          if values &gt; 1: 
              # do something
  </code></pre>
  
  <p>Can I do better? </p>