I need only those company name with year and estimate grp size those are present in all three year eg 2019, 2020, 2021
year Company/Account Name EstimatedGroupSize
0 2019 Unknown 19550
1 2019 Mayo Clinic 7754
2 2019 Deloitte 6432
3 2019 Rizona State 5582
4 2019 Intel Corporation 4595
5 2020 Deloitte 4063
6 2020 Unknown 3490
7 2021 Unknown 3484
8 2020 Intel Corporation 3460
9 2021 Intel Corporation 3433
10 2021 Deloitte 3250
So my output should be
year Company/Account Name EstimatedGroupSize
0 2019 Unknown 19550
2 2019 Deloitte 6432
4 2019 Intel Corporation 4595
5 2020 Deloitte 4063
6 2020 Unknown 3490
7 2021 Unknown 3484
8 2020 Intel Corporation 3460
9 2021 Intel Corporation 3433
10 2021 Deloitte 3250
>Solution :
Here is solution for filter year with Company/Account Name if present at least one row and filter original DataFrame by inner merge:
#if need filter ony some years first
df = df[df['year'].isin([2019, 2020, 2021])]
df1 = pd.crosstab(df['year'], df['Company/Account Name'])
df = df.merge(df1.loc[:, df1.gt(0).all()].stack().index.to_frame(index=False))
print (df)
year Company/Account Name EstimatedGroupSize
0 2019 Unknown 19550
1 2019 Deloitte 6432
2 2019 Intel Corporation 4595
3 2020 Deloitte 4063
4 2020 Unknown 3490
5 2021 Unknown 3484
6 2020 Intel Corporation 3460
7 2021 Intel Corporation 3433
8 2021 Deloitte 3250