title: Consolidate column headings into single "label" column
body: <p>I have a pandas dataframe of the form:</p>
  <pre><code>   Experiment1  Experiment2  Experiment3  Experiment4 ... ExperimentN
  0  39.051650    27.681186    32.278991     31.383350  ...  31.383350
  1  39.051650    27.681186    32.278991     31.383350  ...  31.383350
  2  39.051650    27.681186    32.278991     31.383350  ...  31.383350
  3  39.051650    27.681186    32.278991     31.383350  ...  31.383350
  4  39.051650    27.681186    32.278991     31.383350  ...  31.383350
  5  39.051650    27.681186    32.278991     31.383350  ...  31.383350
  6  39.051650    27.681186    32.278991     31.383350  ...  31.383350
  
  </code></pre>
  <p>Numbers are just placeholders, experiments won't have all constant values in practice. Instead of an independent column for each experiment, I want the column headers to be identifiers in their own &quot;Experiment&quot; column, and to take all the data and place it into one column:</p>
  <pre><code>     Experiment     Values
  0   &quot;Experiment1&quot;  39.051650
  1   &quot;Experiment1&quot;  39.051650
  .         .            .
  .         .            .
  .         .            .
  N-1 &quot;ExperimentN&quot;  31.383350
  N   &quot;ExperimentN&quot;  31.383350
  </code></pre>
  <p>How would I go about doing this?</p>