title: Iteratively building sets of tuples
body: <p>I am trying to iteratively build a set of tuples using <code>set.add(tuple)</code>. The problem is that first tuple does not remain encapsulated as a tuple. Its members enter the set as unique elements.</p>
  
  <pre><code># What I'd like to do
  s = set((1,2))
  s.add((3,4))
  s.add((5,6))
  
  &gt;&gt;&gt;s
  &gt;&gt;&gt;{1, 2, (3, 4), (5, 6)}
  </code></pre>
  
  <p>Of course I can build the whole thing up as a list of tuples and then convert it to a set, but I'd like to know if it is possible to avoid casting from list to set.</p>
  
  <pre><code># Works with some extra work
  l = [(1,2)]
  l.append((3,4))
  l.append((5,6))
  s = set(l)
  
  &gt;&gt;&gt;s
  &gt;&gt;&gt;&gt; {(1, 2), (3, 4), (5, 6)}
  </code></pre>
  
  <p>Thanks.</p>