title: Writing dataframe to csv WITHOUT removing commas
body: <p>I want to write a pandas dataframe to csv.  One of the columns of the df has entries which are lists, e.g. [1, 2], [3, 4], ...</p>
  
  <p>When I use df.to_csv('output.csv') and I open the output csv file, the commas are gone.  That is, the corresponding column of the csv has entries [1  2], [3  4], ....</p>
  
  <p>Is there a way to write a dataframe to csv without removing the commas in these lists?  I've also tried using csv.writer.</p>