calculate conditional probability

Question

Input

cust_Id  category  product  purchased
1        Elec      light    0    
1        Elec      light    1
1        Elec      light    0
1        HA        Table    1
1        HH        Pen      1
2        Elec      light    0
2        HA        Table    1
3        HH        Pen      0
3        Elec      light    1

I want to know the best customer,category,product based on maximum probability value

Answer 1

Try this:

grp = df.groupby(['cust_Id', 'category', 'product'])
prob = grp.sum() / grp.count()

Result is the probability that a particular combination of the 3 attributes will purchase something:

                          purchased
cust_Id category product           
1       Elec     light     0.333333
        HA       Table     1.000000
        HH       Pen       1.000000
2       Elec     light     0.000000
        HA       Table     1.000000
3       Elec     light     1.000000
        HH       Pen       0.000000

The probability of them not purchase anything is simply the complement of that (i.e. 1 - prob)