title: Run into a python error <generator object <genexpr>
body: <p>When I run</p>
  
  <pre><code>a = ["I","love","you"]
  a = {(word) for word in a}
  print a
  </code></pre>
  
  <p>I get this result</p>
  
  <pre><code>set(['I', 'you', 'love'])
  </code></pre>
  
  <p>and that's what I expect.</p>
  
  <p>But when I run</p>
  
  <pre><code>a = ["I","love","you"]
  a = {((word) for word in c)for c in a}
  print a
  </code></pre>
  
  <p>I get some unexpected result:</p>
  
  <pre><code>set([&lt;generator object &lt;genexpr&gt; at 0x1004d5280&gt;, &lt;generator object &lt;genexpr&gt; at 0x1004d5320&gt;, &lt;generator object &lt;genexpr&gt; at 0x1004d5370&gt;])
  </code></pre>
  
  <p>And what I expect is </p>
  
  <pre><code>set(['e','I','u','o','v','l','y')
  </code></pre>
  
  <p>Can anybody tell my the reason that causes this problem?</p>