title: Contains of HashSet<Integer> in Python
body: <p>In Java we have <code>HashSet&lt;Integer&gt;</code>, I need similar structure in Python to use contains like below:</p>
  
  <pre><code>A = [1, 2, 3]
  S = set()
  S.add(2)
  for x in A:
      if S.contains(x):
          print "Example"
  </code></pre>
  
  <p>Could you please help?</p>