title: Is there any numpy group by function?
body: <p>Is there any function in numpy to group this array down below by the first column?</p>
  
  <p>I couldn't find any good answer over the internet..</p>
  
  <pre><code>&gt;&gt;&gt; a
  array([[  1, 275],
         [  1, 441],
         [  1, 494],
         [  1, 593],
         [  2, 679],
         [  2, 533],
         [  2, 686],
         [  3, 559],
         [  3, 219],
         [  3, 455],
         [  4, 605],
         [  4, 468],
         [  4, 692],
         [  4, 613]])
  </code></pre>
  
  <p>Wanted output:</p>
  
  <pre><code>array([[[275, 441, 494, 593]],
         [[679, 533, 686]],
         [[559, 219, 455]],
         [[605, 468, 692, 613]]], dtype=object)
  </code></pre>