title: Contruct 3d array in numpy from existing 2d array
body: <p>During preparing data for NumPy calculate. I am curious about way to construct: </p>
  
  <pre><code>myarray.shape =&gt; (2,18,18)
  </code></pre>
  
  <p>from: </p>
  
  <pre><code>d1.shape =&gt; (18,18)
  d2.shape =&gt; (18,18)
  </code></pre>
  
  <p>I try to use NumPy command:</p>
  
  <pre><code>hstack([[d1],[d2]])
  </code></pre>
  
  <p>but it looks not work!</p>