外部加入两个Pandas Dataframes

Question

我有三个pandas数据框，如下所示：

import pandas as pd
df1=pd.dataFrame ({
                 'Bus':['AM','AM','WM','PC','CC'],\
                 'IC/Third':['IC','Third','Third','IC','Third'],\
                 'Line':['PRV','PRV1','PRV2','PRV3','PRV4'],\
                 'Amount':[100,100,100,100,100]\
                  })
df1=df1.groupby(['Bus','IC/Third','Line']).agg({'Amount':'sum'})
df1.reset_index()

df2=df1.groupby(['Bus','Line']).agg({'Amount':'sum'})
df2.reset_index()

df3=pd.merge(df1,df2,on=['Bus','Line'],how='left')
df3

我正在尝试加入数据帧df1和df2，但收到错误。有什么想法吗？