Assign unique numeric value to each subgroup in pandas

I have a dataframe. I assigned a uniuqe value to each group. But also want to assign a unique value to each element or subgroup of each group.

df = pd.DataFrame({'A':[1,2,3,4,6,3,7,3,2],'B':[4,3,8,2,6,3,9,1,0], 'C':['a','a','c','b','b','b','b','c','c']})

I assigned a unique value to each group as follow

df.groupby('C').ngroup()

But i want output as

index  grp  subgrp
0      0     0
1      0     1
2      2     0
3      1     0
4      1     1
5      1     2
6      1     3
7      2     1
8      2     2

>Solution :

Adding cumcount after get the grp column

df['grp'] = df.groupby('C').ngroup()
df['subgrp'] = df.groupby('grp').cumcount()
df
Out[356]: 
   A  B  C  grp  subgrp
0  1  4  a    0       0
1  2  3  a    0       1
2  3  8  c    2       0
3  4  2  b    1       0
4  6  6  b    1       1
5  3  3  b    1       2
6  7  9  b    1       3
7  3  1  c    2       1
8  2  0  c    2       2