title: Remove `NaN` from Pandas Dataframe by Group
body: <p>I have a Dataframe that looks like this:</p>
  
  <pre><code>value   attribute1  attribute2  attribute3  attribute4
  value1  NaN         NaN         foo         NaN
  value1  bar         NaN         NaN         NaN
  value1  NaN         baz         NaN         NaN
  value1  NaN         NaN         NaN         boo
  </code></pre>
  
  <p>I am trying to find a way to condense the frame so that it looks more like this: </p>
  
  <pre><code>value   attribute1  attribute2  attribute3  attribute4
  value1  bar         baz         foo         boo
  </code></pre>
  
  <p><strong><em>I have not been able to find any specific solutions that will allow me to do this.</em></strong></p>