title: Python sort list of dictionaries, some labels may be missing
body: <p>How do I sort a list of dictionaries where some labels for which I want to sort may be missing?</p>
  
  <p>Specifically, this list is from MPD and looks something like the following...</p>
  
  <pre><code>[{'title':'Bad','album': 'XSCAPE','genre':'Pop'}, {'title': 'Down to', 'album': 'Money'}]
  </code></pre>
  
  <p>I would like to sort by genre, but note the dictionary in the second item has no key for that.</p>
  
  <p>Is there a built in 'Pythonic' way to do this, or will I have to build my own sort algorithm?</p>