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
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