title: Matplotlib: draw grid lines behind other graph elements
body: <p>In Matplotlib, I make dashed grid lines as follows:</p>
  
  <pre><code>fig = pylab.figure()    
  ax = fig.add_subplot(1,1,1)
  ax.yaxis.grid(color='gray', linestyle='dashed')
  </code></pre>
  
  <p>however, I can't find out how (or even if it is possible) to make the grid lines be drawn behind other graph elements, such as bars. Changing the order of adding the grid versus adding other elements makes no difference. </p>
  
  <p>Is it possible to make it so that the grid lines appear behind everything else?</p>