Python Pandas : combine 2 dataframes, 一帧的列作为最终结果的索引

Question

数据帧 df1:

+--------+------+--------+
| userId | isbn | rating |
+--------+------+--------+
|      1 | 0001 |      3 |
|      2 | 0002 |      4 |
|      2 | 0003 |      5 |
+--------+------+--------+

数据帧 df2:

+------+-------+
| isbn | title |
+------+-------+
| 0001 | aaa   |
| 0002 | bbb   |
| 0003 | ccc   |
+------+-------+

我可以将它们合并到:

+-----+-----+-----+
|     |  1  |  2  |
+-----+-----+-----+
| aaa | 3   | NAN |
| bbb | NAN | 4   |
| ccc | NAN | 5   |
+-----+-----+-----+

其中列是userId，索引是标题。 isbn 在合并后被删除。

谢谢。

Answer 1

一旦你merge这些框架，您可以使用pivot_table :

In [11]: merged = df.merge(df2)

In [12]: merged
Out[12]:
   userId  isbn  rating title
0       1     1       3   aaa
1       2     2       4   bbb
2       2     3       5   ccc

In [13]: merged.pivot_table('rating', 'title', 'userId')
Out[13]:
userId   1   2
title
aaa      3 NaN
bbb    NaN   4
ccc    NaN   5