根据条件合并两个DataFrame

Question

我想在两个数据帧之间匹配事实日期和场景条件的基础上合并两个数据帧，然后将altdate列添加到第二个数据帧中。你知道吗

第一个数据帧如下所示：

          fact_date   scen altdate
0        2008-08-18   -1  2008-08-25
1        2008-08-18    0  2008-08-18
2        2008-08-18    1  2008-08-15
3        2008-08-18    2  2008-08-14
4        2008-08-18    3  2008-08-13
5        2008-08-18    4  2008-08-12
6        2008-08-18    5  2008-08-11
7        2008-08-18    6  2008-08-08
8        2008-08-18    7  2008-08-07
9        2008-08-18    8  2008-08-06
...

第二个数据帧如下所示：

          fact_date  flag       scen  values
0        2008-08-18     0       -1   462456.29
1        2008-08-18     0        0  1119881.78
2        2008-08-18     0        1  1922320.74
3        2008-08-18     0        2  3559026.11
4        2008-08-18     0        3  3510447.61
5        2008-08-18     0        4  4873269.42
6        2008-08-18     0        5  5098557.55
7        2008-08-18     0        6  4610888.45
8        2008-08-18     0        7  4090821.69
9        2008-08-18     0        8  4219340.84
...

输出应如下所示：

          fact_date  flag       scen  values     altdate
0        2008-08-18     0       -1   462456.29   2008-08-25
1        2008-08-18     0        0  1119881.78   2008-08-18
2        2008-08-18     0        1  1922320.74   2008-08-15
3        2008-08-18     0        2  3559026.11   2008-08-14
4        2008-08-18     0        3  3510447.61   2008-08-13
5        2008-08-18     0        4  4873269.42   2008-08-12
6        2008-08-18     0        5  5098557.55   2008-08-11
7        2008-08-18     0        6  4610888.45   2008-08-08
8        2008-08-18     0        7  4090821.69   2008-08-07
9        2008-08-18     0        8  4219340.84   2008-08-06
...

Answer 1

我不完全明白你在说什么，但我想你只是想加入。如果你使用熊猫，应该是这样的：

df2 = df2.join(df1,on=['fact_date','scen'],how='left')

希望这有帮助。你知道吗

Answer 2

我会尽力的

df2.merge(df1, on=['fact_date', 'scen'])

它回来了

    fact_date  flag  scen      values     altdate
0  2008-08-18     0    -1   462456.29  2008-08-25
1  2008-08-18     0     0  1119881.78  2008-08-18
2  2008-08-18     0     1  1922320.74  2008-08-15
3  2008-08-18     0     2  3559026.11  2008-08-14
4  2008-08-18     0     3  3510447.61  2008-08-13
5  2008-08-18     0     4  4873269.42  2008-08-12
6  2008-08-18     0     5  5098557.55  2008-08-11
7  2008-08-18     0     6  4610888.45  2008-08-08
8  2008-08-18     0     7  4090821.69  2008-08-07
9  2008-08-18     0     8  4219340.84  2008-08-06