Ashwanth - 2 months ago 5x

Python Question

I wanted to apply a custom operation on a column by grouping the values on another column. Group by column to get the count, then divide the another column value with this count for all the grouped records.

My Data Frame:

`emp opp amount`

0 a 1 10

1 b 1 10

2 c 2 30

3 b 2 30

4 d 2 30

- For opp=1, two emp's worked(a,b). So the amount should be shared like

10/2 =5 - For opp=2, two emp's worked(b,c,d). So the amount should be like

30/3 = 10

Final Output DataFrame:

`emp opp amount`

0 a 1 5

1 b 1 5

2 c 2 10

3 b 2 10

4 d 2 10

What is the best possible to do so

Answer

```
df['amount'] = df.groupby('opp')['amount'].transform(lambda g: g/g.size)
df
# emp opp amount
# 0 a 1 5
# 1 b 1 5
# 2 c 2 10
# 3 b 2 10
# 4 d 2 10
```

Or:

```
df['amount'] = df.groupby('opp')['amount'].apply(lambda g: g/g.size)
```

does similar thing.

Source (Stackoverflow)

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