title: Select rows of numpy.ndarray where the first row number is inside some list
body: <p>I'm looking for a short readable way to select some rows of an 2D numpy.ndarray, where the first number of each row is in some list. </p>
  
  <p>Example: </p>
  
  <pre class="lang-py prettyprint-override"><code>&gt;&gt;&gt; index
  [4, 8]
  
  &gt;&gt;&gt; data 
  array([[ 0,  1,  2,  3],
        [ 4,  5,  6,  7],
        [ 8,  9, 10, 11],
        [12, 13, 14, 15]])
  </code></pre>
  
  <p>So in this case i only need </p>
  
  <pre class="lang-py prettyprint-override"><code> array([[ 4,  5,  6,  7],
         [8,  9, 10, 11]])
  </code></pre>
  
  <p>because the first numbers of these rows are 4 and 8 which are listed in <code>index</code>.  </p>
  
  <p>Basically im looking for something like:</p>
  
  <pre class="lang-py prettyprint-override"><code>data[data[:,0] == i if i in index]
  </code></pre>
  
  <p>which of course is not working.</p>