pandas groupby 列列出并保留某些值

Question

I have the following dataframe:

id       occupations
111      teacher
111      student
222      analyst
333      cook
111      driver
444      lawyer

I create a new column with a list of the all the occupations:

new_df['occupation_list'] = df['id'].map(df.groupby('id')['occupations'].agg(list))

How do I only include teacher and student values in occupation_list ?

Answer 1

You can filter before groupby:

to_map = (df[df['occupations'].isin(['teacher', 'student'])]
             .groupby('id')['occupations'].agg(list)
         )

df['occupation_list'] = df['id'].map(to_map)

Output:

    id occupations     occupation_list
0  111     teacher  [teacher, student]
1  111     student  [teacher, student]
2  222     analyst                 NaN
3  333        cook                 NaN
4  111      driver  [teacher, student]
5  444      lawyer                 NaN

Answer 2

You can also do

df.groupby('id')['occupations'].transform(' '.join).str.split()

Answer 3

You would just do a groupby and agg the column to a list:

df.groupby('id',as_index=False).agg({'occupations':lambda x: x.tolist()})

out:

>>> df
    id occupations
0  111     teacher
1  111     student
2  222     analyst
3  333        cook
4  111      driver
5  444      lawyer
>>> df.groupby('id',as_index=False).agg({'occupations':lambda x: x.tolist()})
    id                 occupations
0  111  [teacher, student, driver]
1  222                   [analyst]
2  333                      [cook]
3  444                    [lawyer]