title: Not plotting 'zero' in matplotlib or change zero to None [Python]
body: <p>I have the code below and I would like to convert all zero's in the data to <code>None</code>'s (as I do not want to plot the data here in matplotlib). However, the code is notworking and <code>0.</code> is still being printed</p>
  
  <pre><code>sd_rel_track_sum=np.sum(sd_rel_track, axis=1)
  for i in sd_rel_track_sum:
     print i
     if i==0:
         i=None
  
  return sd_rel_track_sum
  </code></pre>
  
  <p>Can anyone think of a solution to this. Or just an answer for how I can transfer all 0 to <code>None</code>. Or just not plot the zero values in Matplotlib.</p>