title: How this numpy advance indexing code works?
body: <p>I am learning numpy framework.This piece of code I don't understand.</p>
  
  <pre><code>import numpy as np
  a =np.array([[0,1,2],[3,4,5],[6,7,8],[9,10,11]])
  print(a)
  row = np.array([[0,0],[3,3]])
  col = np.array([[0,2],[0,2]])
  b = a[row,col]
  print("This is b array:",b)
  </code></pre>
  
  <p>This <code>b</code> array returns the corner values of <code>a</code> array, that is, <code>b</code>  equals <code>[[0,2],[9,11]]</code>.</p>