Pandas DataFrame 迭代行和求和

问题描述

我有这个熊猫数据帧:

 recipe_name   ingredient_group       weight%
 pudding       milk                     0.60
 pudding 2     sugar                    0.10
 pudding 2     sugar                    0.70
 pudding 2     milk                     0.30
 pudding 3     egg                      0.20

我想要一个像这样的 Pandas DataFrame:

I would like a pandas DataFrame like this:

 recipe_name   ingredient_group       weight%     new_column
 pudding       milk                     0.60      0.60
 pudding 2     sugar                    0.10      0.80 (0.1+0.7)
 pudding 2     sugar                    0.70      0.80 (0.1+0.7)
 pudding 2     milk                     0.30      0.30
 pudding 3     egg                      0.20      0.20

问题是有些食谱多次使用相同的成分(例如布丁 2 使用 2 倍的糖).

The problem is that there are recipes that use the same ingredient multiple times (for example pudding 2 uses 2 times sugar).

我想创建一个额外的列，其中包含重量百分比，然后是使用两次的成分的总和(参见上面的示例).

I would like to create an extra column with the weight% and then with the sum of an ingredient that was used twice (see example above).

我试图为这个问题做一个 for 循环，但我没有成功.任何人的想法?

I tried to make a for loop for this problem, but I didn't succeed. Anyone an idea?

推荐答案

使用 groupby 与 transform sum:

df['accumulated weight'] = df.groupby(['name','group'])['weight'].transform(sum)
print (df)
    name     group  weight  accumulated weight
0  Appie  elephant      60                  60
1  Henry     tiger      50                 120
2  Henry     tiger      70                 120
3  Laura       cow      30                  30
4  Laura     tiger      20                  20

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