title: Transform array of arrays to a single array
body: <p>I would like to expand a list of arrays into a single array, so for example:</p>
  <pre><code>a = [array([1,2,3]), array([4,5,6]), array([7,8,9,])]
  </code></pre>
  <p>To become:</p>
  <pre><code>a = [array([1,2,3,4,5,6,7,8,9])]
  </code></pre>
  <p>How do I do this?</p>