populate a dense dataframe given a key-value dataframe

populate a dense dataframe given a key-value dataframe

I have a key-value dataframe:
pd.DataFrame(columns=['X','Y','val'],data=
[['a','z',5],['b','g',3],['b','y',6],['e','r',9]])
> X Y val
0 a z 5
1 b g 3
2 b y 6
3 e r 9
Which I'd like to convert into a denser dataframe:
X z g y r
0 a 5 0 0 0
1 b 0 3 6 0
2 e 0 0 0 9
Before I resort to a pure-python I was wondering if there was a simple way
to do this with pandas.