title: Groupby in Reverse
body: <p>I have a pandas dataframe with name of variables, the values for each and the <code>count</code> (which shows the frequency of that row):</p>
  <pre><code>df = pd.DataFrame({'var':['A', 'B', 'C'], 'value':[10, 20, 30], 'count':[1,2,3]})
  
  var  value  count
  A    10     1
  B    20     2
  C    30     3
  </code></pre>
  <p>I want to use <code>count</code> to get an output like this:</p>
  <pre><code>var  value
  A    10
  B    20
  B    20
  C    30
  C    30
  C    30
  </code></pre>
  <p>What is the best way to do that?</p>