How filter two specific values in one column that has a common value in another column

Question

The minimum reproducible example of my data frame looks like this

df = pd.DataFrame({'patient': ['patient1', 'patient1', 'patient1','patient2', 'patient2', 'patient3','patient3','patient4','patient4','patient4','patient4'], 
                   'gene':['TYR','TYR','TYR','TYR','TYR','TYR','TYR','TYR','TYR', 'TYR','TYR'],
                   'variant': ['buu', 'luu', 'stm','lol', 'bla', 'buu', 'lol','buu', 'luu', 'IDK','ploy'],
                    'genotype': ['hom', 'het', 'hom','het', 'hom', 'het', 'het','het', 'hom', 'hom','hom']})

df

 patient gene variant genotype
0   patient1  TYR     buu      hom
1   patient1  TYR     luu      het
2   patient1  TYR     stm      hom
3   patient2  TYR     lol      het
4   patient2  TYR     bla      hom
5   patient3  TYR     buu      het
6   patient3  TYR     lol      het
7   patient4  TYR     ploy     het
8   patient4  TYR     luu      hom
9   patient4  TYR     IDK      hom
10  patient4  TYR     buu      hom

I need to identify patients with the variants "buu" and "luu"

Results

patient1  TYR     buu      hom
patient1  TYR     luu      het
patient4  TYR     luu      hom
patient4  TYR     buu      hom

>Solution :

Group by patient and filter groups keeping those whose variant contains both required variants (buu, luu):

var_set = {'buu', 'luu'}  # set of variants
df[df['variant'].isin(var_set)].groupby('patient')\
    .filter(lambda x: set(x['variant']) >= var_set)

• set(A) >= set(B) gives True when set A is a superset of set B

    patient gene variant genotype
0  patient1  TYR     buu      hom
1  patient1  TYR     luu      het
7  patient4  TYR     buu      het
8  patient4  TYR     luu      hom