是否可以按多索引级别之一对多索引(2 级)pandas 数据框进行分组?
Is it possible to groupby a multi-index (2 levels) pandas dataframe by one of the multi-index levels ?
我知道的唯一方法是在多索引上重置索引，然后再次设置索引.我确信有更好的方法来做到这一点，我想知道如何做.
The only way I know of doing it is to reset_index on a multiindex and then set index again. I am sure there is a better way to do it, and I want to know how.
推荐答案是的，使用 level 参数.看看这里.示例:
Yes, use the level parameter. Take a look here. Example:
In [26]: s first second third bar doo one 0.404705 two 0.577046 baz bee one -1.715002 two -1.039268 foo bop one -0.370647 two -1.157892 qux bop one -1.344312 two 0.844885 dtype: float64 In [27]: s.groupby(level=['first','second']).sum() first second bar doo 0.981751 baz bee -2.754270 foo bop -1.528539 qux bop -0.499427 dtype: float64