如何通过公共列（ID）将两个分组熊猫数据帧合并在一起？

Question

I'm learning data analysis with pandas.

I have two grouped-by dataframes, looking like below.

df1:

        count1  count2  rate
id          
958     34  34  1.000000
2822    41  41  1.000000
5193    180 184 0.978261
5841    35  35  1.000000
5858    104 104 1.000000

df2:

    price
id  
958     170
2822    138
5193    160
5841    181
5858    250

How can I do pd.merge(df1, df2, how='inner', on=['id']) ? Currently, since 'id' is the index, I can't select it. Could someone help?

Answer 1

You could use join

In [226]: df1.join(df2)
Out[226]:
      count1  count2      rate  price
id
958       34      34  1.000000    170
2822      41      41  1.000000    138
5193     180     184  0.978261    160
5841      35      35  1.000000    181
5858     104     104  1.000000    250

or merge by using reset_index of df1 , df2

In [227]: pd.merge(df1.reset_index(), df2.reset_index(), how='inner', on=['id'])
Out[227]:
     id  count1  count2      rate  price
0   958      34      34  1.000000    170
1  2822      41      41  1.000000    138
2  5193     180     184  0.978261    160
3  5841      35      35  1.000000    181
4  5858     104     104  1.000000    250