Python pandas：按日期索引和公共列值組合兩個數據幀

Question

有兩個日期幀，一個是df1，另一個是df2，如下所示：

DF1：

               a   b    id
2010-01-01     1   4    21
2010-01-01     2   5    22
2010-01-01     3   6    23
2010-01-01     4   7    24
2010-01-02     1   4    21
2010-01-02     2   5    22
2010-01-02     3   6    23
2010-01-02     4   7    24
2010-01-03     1   4    21
2010-01-03     2   5    22
2010-01-03     3   6    23
2010-01-03     4   7    24
...........................

DF2：

               c   d    id
2010-01-02     1   4    21
2010-01-02     2   5    22
2010-01-02     3   6    23
2010-01-02     4   7    24
2010-01-03     1   4    21
2010-01-03     2   5    22
2010-01-03     3   6    23
2010-01-03     4   7    24
...........................

我想通過公共索引合並或連接兩個數據幀（請注意df1中的某些索引不在df2中）和id，我期望一個連接的數據幀如下

               c   d    a   b   id
2010-01-02     1   4    1   4   21
2010-01-02     2   5    2   5   22
2010-01-02     3   6    3   6   23
2010-01-02     4   7    4   7   24
2010-01-03     1   4    1   4   21
2010-01-03     2   5    2   5   22
2010-01-03     3   6    3   6   23
2010-01-03     4   7    4    7  24

我使用了以下代碼

 df = df1.join(df2, on = ['id'], how='inner')

但那沒用

Answer 1

IIUC：

In [388]: df2.set_index('id', append=True).join(df1.set_index('id', append=True)) \
             .reset_index(level='id')
Out[388]:
            id  c  d  a  b
2010-01-02  21  1  4  1  4
2010-01-02  22  2  5  2  5
2010-01-02  23  3  6  3  6
2010-01-02  24  4  7  4  7
2010-01-03  21  1  4  1  4
2010-01-03  22  2  5  2  5
2010-01-03  23  3  6  3  6
2010-01-03  24  4  7  4  7