title: Pandas GroupBy Join Strings Multiple Columns
body: <p>Could somebody tell me how to simplify this piece of code? It is archaic to write all the column names, specially on wide tables. For some reason if I run <code>df.groupby('APID').agg(','.join)</code> it does not return all the columns. Only the first 3. All the columns are of type <code>'object'</code>.</p>
  
  <pre><code>df.groupby('APID').agg(
      {'Names':','.join,
       'Alias_Name':','.join,
       'APID':','.join,
       'Prev_Rep':','.join,
       'Rep_Assigned':','.join,
       'City':','.join,
       'State':','.join,
       'Zip_Code':','.join,
       'Country':','.join,
       'Distribution_Numbers':','.join,
       'Partnership':','.join,
       'Onboarding':','.join,}
  )
  </code></pre>