title: Pandas select rows where columns are dynamic and a single column's value is greater than zero
body: <p>Assume a DataFrame is created where the number of columns and column names is dynamic.
  So you could have a DataFrame like:</p>
  
  <pre><code>two = pd.DataFrame({'one' : pd.Series([10, 0, 10], index=['a', 'b', 'c']),
     'two' : pd.Series([0, 0, 10.], index=['a', 'b', 'c'])})
  
   one   two
  a   10   0.0
  b    0   0.0
  c   10  10.0
  </code></pre>
  
  <p>Or you could have a Dataframe like:</p>
  
  <pre><code>three = pd.DataFrame({'blue' : pd.Series([10, 0, 10], index=['a', 'b', 'c']),
     'red' : pd.Series([0, 0, 10], index=['a', 'b', 'c']),
     'two' : pd.Series([0, 0, 10], index=['a', 'b', 'c'])})
  
     blue  red  two
  a    10    0    0
  b     0    0    0
  c    10   10   10
  </code></pre>
  
  <p>So you won't know how many columns or the column names until run time. There is no limit on number of columns.</p>
  
  <p>How do you select rows where only one column is greater than zero? </p>
  
  <p>So for a given row if all column values are zero or if more than one column value is greater than zero its excluded from selection.</p>
  
  <p>From the two above examples I'd respectfully output:</p>
  
  <pre><code>   one  two
  a   10    0
  </code></pre>
  
  <p>and </p>
  
  <pre><code>   blue  red  two
  a    10    0    0
  </code></pre>