title: Merge Multiple Columns As New Rows in Pandas Dataframe
body: <p>I am trying to unroll a list within a column to add more rows for the purpose of feeding it into a swarmplot.</p>
  
  <p>Right now, I build a dictionary of lists:</p>
  
  <pre><code># store all list of metrics
  clf_aucs = dict()
  _list = np.arange(0, 500) # build dummy list of floats
  clf_aucs[id] = _list
  </code></pre>
  
  <p>This dictionary is say 5 keys, each with a list of 500 floats. When I next create a dataframe:</p>
  
  <pre><code>clf_aucs_df = pd.DataFrame(clf_aucs, 
                            ).transpose()
  clf_aucs_df = clf_aucs_df.reset_index()
  display(clf_aucs_df.head())
  print(clf_aucs_df.shape)
  </code></pre>
  
  <p>The result would look like:</p>
  
  <pre><code>index   0   1   2   3   4   5   6   7   8   ... 490 491 492 493 494 495 496 497 498 499
  0   clf0    0.432609    0.398760    0.292517    0.411905    0.385375    0.390023    0.364286    0.364035    0.450000    ... 0.477273    0.355372    0.378000    0.386667    0.396104    0.395085    0.426667    0.461957    0.402746    0.445238
  1   clf1    0.432900    0.231602    0.416149    0.365217    0.414286    0.461039    0.325217    0.357143    0.447826    ... 0.402893    0.323913    0.420949    0.434783    0.372294    0.360417    0.410208    0.420949    0.392857    0.343685
  2   clf2    0.322314    0.400000    0.409524    0.405797    0.466942    0.383399    0.478261    0.405896    0.432892    ... 0.371542    0.494318    0.493750    0.415238    0.414079    0.400433    0.402778    0.493478    0.478261    0.458498
  3   clf3    0.509921    0.579051    0.545455    0.658103    0.576560    0.500000    0.515810    0.505682    0.525880    ... 0.590909    0.553360    0.409938    0.462585    0.584348    0.575397    0.472332    0.513834    0.587500    0.612500
  4   clf4    0.474206    0.490451    0.479437    0.593750    0.545455    0.580357    0.484127    0.596273    0.537549    ... 0.665909    0.545351    0.609375    0.556277    0.531522    0.511905    0.583851    0.543478    0.513889    0.583333
  5 rows × 501 columns
  </code></pre>
  
  <p>My question is how can I merge the columns 0-499, so that the new dataframe would be 2500 rows x 2 column with the id-column, and the numerical column. </p>
  
  <p>Other attempts:</p>
  
  <ol>
  <li>tried different ways of creating a dataframe from list of lists</li>
  <li>looked at merge/join, but this in general seemed to be geared
  towards "combining" separate dataframes and adding columns</li>
  </ol>