Python：基于组的求和并将其显示为附加列

Question

Say we have a dataframe like the one below:

channel     store          units
Offline     Bournemouth    62
Offline     Kettering      90
Offline     Manchester     145
Online      Bournemouth    220
Online      Kettering      212
Online      Manchester     272

My purpose would be to add two more columns containing the full amount of units sold for each channel and the share each store represents within each one. In short, the output I desire to reach should look as follows:

channel     store          units   units_per_channel  store_share
Offline     Bournemouth    62      297                0.21
Offline     Kettering      90      297                0.30
Offline     Manchester     145     297                0.49
Online      Bournemouth    220     704                0.31
Online      Kettering      212     704                0.30
Online      Manchester     272     704                0.39

Is there any simple and elegant way to get this?

Answer 1

Do a .grouby() on the channel , and get the sum of the units . Then simply divide the units by units_per_channel

import pandas as pd


df = pd.DataFrame([['Offline',    'Bournemouth',    62],
['Offline' ,    'Kettering'  ,    90],
['Offline' ,    'Manchester' ,    145],
['Online'  ,    'Bournemouth',    220],
['Online'  ,    'Kettering',      212],
['Online'  ,    'Manchester',     272]],
                  columns=['channel','store','units'],)


df['units_per_channel'] = df.groupby('channel')['units'].transform('sum')
df['store_share'] = df['units'] / df['units_per_channel']

Output:

print(df)
   channel        store  units  units_per_channel  store_share
0  Offline  Bournemouth     62                297     0.208754
1  Offline    Kettering     90                297     0.303030
2  Offline   Manchester    145                297     0.488215
3   Online  Bournemouth    220                704     0.312500
4   Online    Kettering    212                704     0.301136
5   Online   Manchester    272                704     0.386364