title: Number of column values greater than 0 for given row?
body: <p>I have a dataframe which looks like:</p>
  
  <pre><code>col1  col2  col3
  0     0     .4
  .3    1     0
  0     0     .8
  </code></pre>
  
  <p>I'd like to create a new column which counts the number of column values greater than 0 in the other three rows:</p>
  
  <pre><code>col1  col2  col3  col4
  0     0     .4    1
  .3    1     0     2
  0     0     .8    1
  </code></pre>