title: Elementwise aggregation (average) of values in a list of numpy arrays with same shape
body: <p>I have a list of numpy arrays. I want to calculate the average of values in these arrays.
  For example:</p>
  
  <pre><code>import numpy as np
  arrays = [np.random.random((4,2)) for _ in range(3)]
  </code></pre>
  
  <p>How can I have the average of elements in this array?</p>
  
  <p>That is I want the results to be of shape <code>(4,2)</code> where each element is the average of corresponding indices for arrays in the list.
  I know I can write a for loop to achieve this, but there should be a better numpy way.</p>