title: Concatenate only extant non-empty numpy arrays?
body: <p>This should be easy...</p>
  
  <p>I want to concatenate arrays A, B and C. It is possible that one or more of them may not exist or be empty. I want the remaining arrays to be concatenated. If, for example, B is empty, I want to concatenate A with C.</p>
  
  <p>I've read these questions that seem relevant:</p>
  
  <p><a href="https://stackoverflow.com/questions/11295609/how-can-i-check-whether-the-numpy-array-is-empty-or-not">How can I check whether the numpy array is empty or not?</a></p>
  
  <p><a href="https://stackoverflow.com/questions/3157374/how-do-you-remove-a-numpy-array-from-a-list-of-numpy-arrays">How do you &#39;remove&#39; a numpy array from a list of numpy arrays?</a></p>
  
  <p>I assume there's a 1-2 line way to do this.</p>