title: Attach two 3d numpy arrays in Python
body: <p>I was wondering how I can attach two 3d numpy arrays in python?</p>
  
  <p>For example, I have one with shape <code>(81,81,61)</code> and I would like to get instead a <code>(81,81,122)</code> shape array by attaching the original array to itself in the z direction.</p>