title: Concatenate 3-d arrays python
body: <p>I want to concatenate empty 3d numpy array</p>
  
  <pre><code>   #2d array works 
     xs = np.array([[1,2,3,4,5],[10,20,30,40,50]])
     ys = np.array([]).reshape(0,5)
     zs = np.vstack([ys, xs])
  
     #3D does not work
     bb = np.array([]).reshape(1080, 1920, 0) # empty 
  
     ss = np.random.rand(1080, 1920,2) #
  
     dd = np.vstack([bb, ss]) # generate an error
  </code></pre>
  
  <p>It is possible to do that ?</p>