通過熊貓的另一列的總和制作一個分組列

Question

我有這個數據集：

+===+=======+======+=======+=======+
|   | Group | Cost | Name1 | Name2 |
+===+=======+======+=======+=======+
| 0 | G1    | 1574 | N1A   | N2A   |
+---+-------+------+-------+-------+
| 1 | G2    | 1322 | N1B   | N2B   |
+---+-------+------+-------+-------+
| 2 | G3    | 1188 | N1C   | N2C   |
+---+-------+------+-------+-------+
| 3 | G3    |  942 | N1D   | N2D   |
+---+-------+------+-------+-------+
| 4 | G4    |  838 | N1E   | N2E   |
+---+-------+------+-------+-------+
| 5 | G5    |    5 | N1F   | N2F   |
+---+-------+------+-------+-------+
| 6 | G5    |    4 | N1F   | N2G   |
+---+-------+------+-------+-------+
| 7 | G5    |    3 | N1G   | N2H   |
+---+-------+------+-------+-------+

現在我想按“組”分組並添加一個分組列，其中包含每個組的“成本”列的總和。 不知道怎么解釋，所以這是預期的結果：

+===+=======+======+======+=======+=======+
|   | Group | Sum  | Cost | Name1 | Name2 |
+===+=======+======+======+=======+=======+
| 0 | G1    | 1574 | 1574 | N1A   | N2A   |
+---+-------+------+------+-------+-------+
| 1 | G2    | 1322 | 1322 | N1B   | N2B   |
+---+-------+------+------+-------+-------+
| 2 | G3    | 2130 | 1188 | N1C   | N2C   |
|   |       |      +------+-------+-------+
|   |       |      |  942 | N1D   | N2D   |
+---+-------+------+------+-------+-------+
| 3 | G4    |  838 |  838 | N1E   | N2E   |
+---+-------+------+------+-------+-------+
| 4 | G5    |   12 |    5 | N1F   | N2F   |
|   |       |      +------+-------+-------+
|   |       |      |    4 | N1F   | N2G   |
|   |       |      +------+-------+-------+
|   |       |      |    3 | N1G   | N2H   |
+---+-------+------+------+-------+-------+

我怎樣才能用熊貓實現這一目標？ 這甚至可能嗎？ 對不起，我是這個東西的新手

Answer 1

使用GroupBy.transform與sum ，然后顯示自己的方式建立MultiIndex由DataFrame.set_index ，但'missing'的價值觀MulitIndex只是不displaing：

df['Sum'] = df.groupby('Group')['Cost'].transform('sum')
df = df.set_index(['Group','Sum','Cost'])

或者：

df1 = (df.assign(Sum = df.groupby('Group')['Cost'].transform('sum'))
         .set_index(['Group','Sum','Cost']))