Groupby class and count missing values in features

Question

I have a problem and I cannot find any solution in the web or documentation, even if I think that it is very trivial.

What do I want to do?

I have a datafram

Answer 1

You can use set_index and sum:

df.set_index('CLASS').isna().sum(level=0)

Output:

       FEATURE1  FEATURE2  FEATURE3
CLASS                              
X           1.0       1.0       2.0
B           0.0       0.0       0.0