title: creating a boolean array which compares numpy elements to None
body: <p>I have a numpy array with dtype=object, and I want to create a boolean array identifying which elements are <code>None</code>. But it looks like <code>None</code> behaves differently...</p>
  
  <pre><code>a = np.array(['Duck','Duck','Duck','Goose',None,1,2,3,1,3,None,4])
  print a == 'Duck'
  print a == 3
  print a == None
  </code></pre>
  
  <p>which results in </p>
  
  <pre><code>[ True  True  True False False False False False False False False False]
  [False False False False False False False  True False  True False False]
  False
  </code></pre>
  
  <p>Is there an "numpythonic" way to get a boolean array of the <code>None</code> elements? I can use </p>
  
  <pre><code>np.array([x is None for x in a])
  </code></pre>
  
  <p>but this seems like there should be a better way.</p>