Given the below column:
     col 
  0  NaN
  1  Jan,Apr,Jul,Oct
  2  Jan,Jun,Jul
  3  Apr,May,Oct,Nov
  4  NaN
  ...
How to convert the months abbreviation to month number (int)? and replace tghe comma with a hyphen? The output should look like:
     col 
  0  NaN
  1  01-04-07-10
  2  01-06-07
  3  04-05-10-11
  4  NaN
  ...
 
    