title: how to append a array to a np.array?
body: <pre><code>coordinates =  np.empty([0,5])
  np.vstack(  (coordinates,  np.array([1, 2, 3, 4, 5]) ))
  print coordinates  # []
  np.append(coordinates, np.array([1, 2, 3, 4, 5]), axis=0)
  print coordinates
  </code></pre>
  
  <p>In the code shown above, I tried to append the array, but both approaches failed. In the first approach, the output is still empty, in the second approach, the output is an error saying</p>
  
  <blockquote>
    <p>ValueError: all the input arrays must have same number of dimensions</p>
  </blockquote>
  
  <p>What is wrong with my method? </p>