python - Pandas groupby for zero values

Question

I have data like this in a csv file

Symbol  Action  Year
  AAPL     Buy  2001
  AAPL     Buy  2001
   BAC    Sell  2002
   BAC    Sell  2002

I am able to read it and groupby like this

df.groupby(['Symbol','Year']).count()

I get

             Action
Symbol Year        
AAPL   2001       2
BAC    2002       2

I desire this (order does not matter)

             Action
Symbol Year        
AAPL   2001       2
AAPL   2002       0
BAC    2001       0
BAC    2002       2

I want to know if its possible to count for zero occurances

Answer 1

You can use this:

df = df.groupby(['Symbol','Year']).count().unstack(fill_value=0).stack()
print (df)

Output:

             Action
Symbol Year        
AAPL   2001       2
       2002       0
BAC    2001       0
       2002       2