dataframe groupby and count nan code example

Example: count nans after groupby pandas

A      B     C
0  foo    one   NaN
1  bar    one  bla2
2  foo    two   NaN
3  bar  three  bla3
4  foo    two   NaN
5  bar    two   NaN
6  foo    one   NaN

df2 = df.C.isnull().groupby([df['A'],df['B']]).sum().astype(int).reset_index(name='count')
print (df2)
     A      B  count
0  bar    one      0
1  bar  three      0
2  bar    two      1
3  foo    one      2
4  foo  three      1
5  foo    two      2