title: How to use numpy with 'None' value in Python?
body: <p>I'd like to calculate the mean of an array in Python in this form:</p>
  
  <pre><code>Matrice = [1, 2, None]
  </code></pre>
  
  <p>I'd just like to have my <code>None</code> value ignored by the <code>numpy.mean</code> calculation but I can't figure out how to do it.</p>