Pandas group by row to sum columns, and return with the least two

Question

A data frame as below:

I want to find out the least 2 project names from the sum of projects’.
Like:

David ['Project_C', 'Project_D']
Kate  ['Project_B', 'Project_D']
Mike  ['Project_A', 'Project_B', 'Project_D']

Here is what I come up with:

import pandas as pd
from io import StringIO

csvfile = StringIO(
"""Name Project_A   Project_B   Project_C   Project_D
David   1       1   
David       1       
David   1   1       1
Mike    1       1   
Mike        1   1   
Kate    1       1   
Kate    1   1   1   1
Kate    1       1   
Kate        1       
""")

dict_p = {0 : 'Project_A',
1: 'Project_B',
2: 'Project_C',
3: 'Project_D'}

df = pd.read_csv(csvfile, sep = 't', engine='python')

df = df.fillna(0)

df = df.groupby(['Name'])["Project_A", "Project_B", "Project_C", "Project_D"].apply(lambda x : x.astype(int).sum())

print (df)

# turn the interim result into a list, then index the smallest 2, and map from dict_p.
dict_from_df = df.set_index('Name').T.to_dict('list')
n_min_values = 2

for k,v in dict_from_df.items():
    index_of_smallest_two = sorted(range(len(v)), key=lambda k: v[k])[:n_min_values] 

    C = (pd.Series(index_of_smallest_two)).map(dict_p)
    final_list = list(C)

    print (k, final_list)

Interim output:

    Name  Project_A  Project_B  Project_C  Project_D
0  David          2          2          1          1
1   Kate          3          2          3          1
2   Mike          1          1          2          0

Final output:

David ['Project_C', 'Project_D']
Kate ['Project_D', 'Project_B']
Mike ['Project_D', 'Project_A']

Mike is missing ‘Project_B’, but Mike’s Project_A and Project_B are both of 1. i.e. it should be Mike [‘Project_D’, ‘Project_A’, ‘Project_B’]

How can I correct it?

Asked By: Mark K

||

Source

Answer 1

One way using pandas.DataFrame.apply with pandas.Series.nsmallest:

gdf = df.groupby("Name").sum()
new_df = gdf.apply(lambda x: list(x.nsmallest(2, keep="all").index), axis=1)
print(new_df)

Output:

Name
David               [Project_C, Project_D]
Kate                [Project_D, Project_B]
Mike     [Project_D, Project_A, Project_B]
dtype: object

Answered By: Chris

Pandas group by row to sum columns, and return with the least two

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