title: How to count non NaN values accross columns in pandas dataframe?
body: <p>My data looks like this:</p>
  
  <pre><code>            Close   a   b   c   d   e   Time    
  2015-12-03  2051.25 5   4   3   1   1   05:00:00    
  2015-12-04  2088.25 5   4   3   1   NaN 06:00:00
  2015-12-07  2081.50 5   4   3   NaN NaN 07:00:00
  2015-12-08  2058.25 5   4   NaN NaN NaN 08:00:00
  2015-12-09  2042.25 5   NaN NaN NaN NaN 09:00:00
  </code></pre>
  
  <p>I need to count 'horizontally' the values in the columns ['a'] to ['e'] that are not NaN. So the outcome would be this:</p>
  
  <pre><code>df['Count'] = .....
  df
  
              Close   a   b   c   d   e   Time     Count
  2015-12-03  2051.25 5   4   3   1   1   05:00:00 5  
  2015-12-04  2088.25 5   4   3   1   NaN 06:00:00 4
  2015-12-07  2081.50 5   4   3   NaN NaN 07:00:00 3
  2015-12-08  2058.25 5   4   NaN NaN NaN 08:00:00 2
  2015-12-09  2042.25 5   NaN NaN NaN NaN 09:00:00 1
  </code></pre>
  
  <p>Thanks</p>