title: How to get a np.ndarray shallow copy with indexing?
body: <p>I have a np.ndarray,and using mask to get a subset:</p>
  <pre><code>a = np.arange(9)
  b = a[[0,2,4]]
  # or 
  c = a[a%2==0]
  </code></pre>
  <p>What I want to do is ensure synchronous modification between the two. If I change the elements of <code>a</code>, I want <code>b</code> and <code>c</code> change simultaneously.</p>
  <pre><code>a[0] = 9
  b[0]==c[0]==9 # True
  </code></pre>
  <p>In addition, I actually using structured array or recarray, how to make sure I shallow copy subset of those two type of array?</p>