title: Delete list (inside a column) with more than one element and transform it to regular column - Pandas
body: <p>I have the dataframe which looks as this:</p>
  
  <pre><code> id 
  444343                           [2]
  50224018                         [7]
  4284                             [2]
  226818                         [2, 36]
  28484                       [29, 15, 52114, 47]
  229261                          [20]
  </code></pre>
  
  <p>This dataframe is consequence of this line of code:</p>
  
  <pre><code>df= df.groupby('id').station.unique()
  </code></pre>
  
  <p>which gave me the unique stations for each group inside the dataframe.
  Now I need to delete all rows that have more than one station, and to convert this row to the regular integer number. For the concrete example:</p>
  
  <pre><code> ID                            station
  444343                           2
  50224018                         7
  4284                             2
  229261                          20
  </code></pre>
  
  <p>But I can't even access to this column, I tried to add it name <code>df.columns = ["number_from", "station"]</code>, to access it with index.. Nothing. -.-</p>