python的groupby方法

group by （）方法以后
df_power.groupby(by=['id']) --

报错：
Can only merge Series or DataFrame objects, a <class 'pandas.core.groupby.generic.DataFrameGroupBy'> was passed

修改成

df_day_original = df_power.groupby(by=['id']).agg('id').reset_index()

报错：

Can only merge Series or DataFrame objects, a <class 'pandas.core.groupby.generic.SeriesGroupBy'> was passed

解决办法：分开写

df_power.groupby(by=['id'])
df_day_original = df_power.reset_index()