title: numpy: can values not be assigned to a sub-array?
body: <pre><code>import numpy as np
  
  a = np.zeros((3,2))
  ind_row = np.array([0,1])    
  a[ind_row, 1]=3
  </code></pre>
  
  <p>now, <code>a</code> is, as expected:</p>
  
  <pre><code> [[ 0.  3.]
   [ 0.  3.]
   [ 0.  0.]]
  </code></pre>
  
  <p>I want to assign a value to a sub-array of <code>a[ind_row, 1]</code>, and expect to be able to do this as follows:</p>
  
  <pre><code>a[ind_row, 1][1] = 5
  </code></pre>
  
  <p>However, this leaves <code>a</code> unchanged! Why should I expect this? </p>