title: pandas: conditional count across row
body: <p>I have a dataframe that has months for columns, and various departments for rows. </p>
  
  <pre><code>                2013April  2013May  2013June
          Dep1        0         10        15
          Dep2        10        15        20
  </code></pre>
  
  <p>I'm looking to add a column that counts the number of months that have a value greater than 0. Ex:</p>
  
  <pre><code>                2013April  2013May  2013June  Count&gt;0 
          Dep1        0         10        15       2
          Dep2        10        15        20       3
  </code></pre>
  
  <p>The number of columns this function needs to span is variable. I think defining a function then using .apply is the solution, but I can't seem to figure it out.</p>