title: Extract indices of cells meeting criteria from pandas DataFrame
body: <p>I have a DataFrame in pandas like this:</p>
  
  <pre><code>  a b c
  A 1 2 3 
  B 4 5 6
  C 7 8 9
  </code></pre>
  
  <p>I want to extract the pairs of index name and column name whose cell has a value bigger than 6.</p>
  
  <p>In other words, I want to obtain</p>
  
  <pre><code>[["B","c"], ["C","a"], ["C","b"], ["C","c"]]
  </code></pre>
  
  <p>Is there any smart way to do this?</p>