title: Why doesn't Python 2.6 have set literals and comprehensions or dict comprehensions?
body: <p>Python 2.6 was basically a stepping stone to make converting to Python 3 easier.  A lot of the features destined for Python 3 were implemented in 2.6 if they didn't break backward compatibility with syntax and the class libs.</p>
  
  <p>Why weren't set literals (<code>{1, 2, 3}</code>), set comprehensions (<code>{v for v in l}</code>), or dict comprehensions (<code>{k: v for k, v in d}</code>) among them?  In particular dict comprehensions would have been a great boon... I find myself using the considerably uglier <code>dict([(k, v) for k, v in d])</code> an awful lot lately.</p>
  
  <p>Is there something obvious I'm missing, or was this just a feature that didn't make the cut?</p>