title: Python pandas remove duplicate rows that have a column value "NaN"
body: <p>The need to rows that have NaN values in them but are also duplicates. For example this table:</p>
  
  <pre><code>    A   B   C
  0   foo 2   3
  1   foo nan nan
  2   foo 1   4
  3   bar nan nan
  4   foo nan nan
  </code></pre>
  
  <p>Should become this:</p>
  
  <pre><code>    A   B   C
  0   foo 2   3
  2   foo 1   4
  3   bar nan nan
  </code></pre>
  
  <p>How can i do that?</p>