pandas Groupby和总和只有一栏 [英] Pandas Groupby and Sum Only One Column

问题描述

所以我有一个数据帧df1，看起来像下面的样子:

So I have a dataframe, df1, that looks like the following:

       A      B      C
1     foo    12    California
2     foo    22    California
3     bar    8     Rhode Island
4     bar    32    Rhode Island
5     baz    15    Ohio
6     baz    26    Ohio

我想按A列分组，然后对B列求和，同时将值保留在C列中.

I want to group by column A and then sum column B while keeping the value in column C. Something like this:

      A       B      C
1    foo     34    California
2    bar     40    Rhode Island
3    baz     41    Ohio

问题是，当我说df.groupby('A').sum()列C被删除时返回

The issue is, when I say df.groupby('A').sum() column C gets removed returning

      B
A
bar  40
baz  41
foo  34

当我进行分组和求和时，如何解决此问题并保留C列?

How can I get around this and keep column C when I group and sum?

推荐答案

执行此操作的唯一方法是将C包含在groupby中(groupby函数可以接受列表).

The only way to do this would be to include C in your groupby (the groupby function can accept a list).

尝试一下:

df.groupby(['A','C'])['B'].sum()

要注意的另一件事是，如果需要在聚合后使用df，则还可以使用as_index = False选项返回数据框对象.当我第一次和熊猫一起工作时，这给我带来了麻烦.示例:

One other thing to note, if you need to work with df after the aggregation you can also use the as_index=False option to return a dataframe object. This one gave me problems when I was first working with Pandas. Example:

df.groupby(['A','C'], as_index=False)['B'].sum()

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