Dataframe creating columns with rows

Question

Restructure the df using col values and missing values should be replaced with 0.

my df :

a     b                 c       

0     AM                24
1     AM                20
4     AM                3
6     AM                2
0     AY                13
1     AY                16
2     AY                1
4     AY                5
6     AY                2

Desired df:

b     0    1   2  4   6 

AM    24   20  0  3   2 
Ay    13   16  1  5   2      

Thanks!!