Adding values for missing data combinations in Pandas

Question

I\'ve got a pandas data frame containing something like the following:

person_id   status    year    count
0           \'pass\'    1980    4
0           \'fa         


        

Answer 1

create a MultiIndex by MultiIndex.from_product() and then set_index(), reindex(), reset_index().

import pandas as pd
import io

all_person_ids = [0, 1, 2]
all_statuses = ['pass', 'fail']
all_years = [1980, 1981, 1982]
df = pd.read_csv(io.BytesIO("""person_id   status    year    count
0           pass    1980    4
0           fail    1982    1
1           pass    1981    2"""), delim_whitespace=True)
names = ["person_id", "status", "year"]

mind = pd.MultiIndex.from_product(
    [all_person_ids, all_statuses, all_years], names=names)
df.set_index(names).reindex(mind, fill_value=0).reset_index()