pandas 根据另一列的唯一值对列的值求和

Sum values of column based on the unique values of another column

提问by user_01

I have a data frame of

我有一个数据框

Column1  Column2
1          20
2          25
3          30
2          40
4          18
1          24

and I want to sum Column2 based on the unique values of Column1. We can find sum based on a specific value such as 1 using this way:

我想根据 Column1 的唯一值对 Column2 求和。我们可以使用这种方式找到基于特定值（例如 1）的总和：

df.loc[df['Column1'] == 1, 'Column2'].sum()

which correctly gives us 44. But how we can do it for all unique values in Column1 such that it produces this one

这正确地给了我们 44。但是我们如何为 Column1 中的所有唯一值执行它，以便它产生这个

Column1  Column2
1          44
2          65
3          30
4          18

回答by W Stokvis

I believe you're looking for groupby. You can find documentation here

我相信你正在寻找groupby。您可以在此处找到文档

df.groupby('Column1')['Column2'].sum()
Column1  Column2
1          44
2          65
3          30
4          18