我有一个如下所示的df。它具有每个月1-12的费用。我想用每12行（第1-12个月）的“费用”总和的百分比创建一个新列。因此，它将花费12行的总和，然后从“成本”中的值计算百分比。 我真的不知道从哪里开始。感谢您的帮助！
输入：
| Name | Month | Costs |
|----------|--------|-------|
| Painting | 1 | 1000 |
| Painting | 2 | 0 |
| Painting | 3 | 0 |
| Painting | 4 | 0 |
| Painting | 5 | 1000 |
| Painting | 6 | 0 |
| Painting | 7 | 0 |
| Painting | 8 | 0 |
| Painting | 9 | 1000 |
| Painting | 10 | 0 |
| Painting | 11 | 0 |
| Painting | 12 | 1000 |
| Repair | 1 | 0 |
| Repair | 2 | 0 |
| Repair | 3 | 0 |
| Repair | 4 | 2500 |
| Repair | 5 | 0 |
| Repair | 6 | 0 |
| Repair | 7 | 5000 |
| Repair | 8 | 0 |
| Repair | 9 | 0 |
| Repair | 10 | 2500 |
| Repair | 11 | 0 |
| Repair | 12 | 0 |
想要的输出：
| Name | Period | Costs | Percentages |
|----------|--------|-------|-------------|
| Painting | 1 | 1000 | 25% |
| Painting | 2 | 0 | 0% |
| Painting | 3 | 0 | 0% |
| Painting | 4 | 0 | 0% |
| Painting | 5 | 1000 | 25% |
| Painting | 6 | 0 | 0% |
| Painting | 7 | 0 | 0% |
| Painting | 8 | 0 | 0% |
| Painting | 9 | 1000 | 25% |
| Painting | 10 | 0 | 0% |
| Painting | 11 | 0 | 0% |
| Painting | 12 | 1000 | 25% |
| Repair | 1 | 0 | 0% |
| Repair | 2 | 0 | 0% |
| Repair | 3 | 0 | 0% |
| Repair | 4 | 2500 | 25% |
| Repair | 5 | 0 | 0% |
| Repair | 6 | 0 | 0% |
| Repair | 7 | 5000 | 50% |
| Repair | 8 | 0 | 0% |
| Repair | 9 | 0 | 0% |
| Repair | 10 | 2500 | 25% |
| Repair | 11 | 0 | 0% |
| Repair | 12 | 0 | 0% |
答案 0 :(得分：5)
尝试transform
df['PCT']=df['Costs']/df.groupby('Name')['Costs'].transform('sum')
df
Out[98]:
Name Month Costs PCT
0 Painting 1 1000 0.25
1 Painting 2 0 0.00
2 Painting 3 0 0.00
3 Painting 4 0 0.00
4 Painting 5 1000 0.25
5 Painting 6 0 0.00
6 Painting 7 0 0.00
7 Painting 8 0 0.00
8 Painting 9 1000 0.25
9 Painting 10 0 0.00
10 Painting 11 0 0.00
11 Painting 12 1000 0.25
12 Repair 1 0 0.00
13 Repair 2 0 0.00
14 Repair 3 0 0.00
15 Repair 4 2500 0.25
16 Repair 5 0 0.00
17 Repair 6 0 0.00
18 Repair 7 5000 0.50
19 Repair 8 0 0.00
20 Repair 9 0 0.00
21 Repair 10 2500 0.25
22 Repair 11 0 0.00
23 Repair 12 0 0.00