python - 根据索引将 pandas 列从数据帧合并到另一个数据帧

Question

我有一个数据框，df_one，看起来像这样，其中video_id是索引:

+----------+--------------+---------------+--------------+----------------+---------------+------------------+
|          | video_length | feed_position | time_watched | unique_watched | count_watched | avg_time_watched |
+----------+--------------+---------------+--------------+----------------+---------------+------------------+
| video_id |              |               |              |                |               |                  |
| 5        |           17 | 12.000000     |           17 |              1 |             1 | 1.000000         |
| 10       |           22 | 10.000000     |            1 |              1 |             1 | 0.045455         |
| 15       |           22 | 13.000000     |           22 |              1 |             1 | 1.000000         |
| 22       |           29 | 20.000000     |            5 |              1 |             1 | 0.172414         |
+----------+--------------+---------------+--------------+----------------+---------------+------------------+

我还有另一个数据帧 df_two ，它看起来像这样，其中 video_id 也是索引:

+----------+--------------+---------------+--------------+----------------+------------------------+
|          | video_length | feed_position | time_watched | unique_watched | count_watched_yeterday |
+----------+--------------+---------------+--------------+----------------+------------------------+
| video_id |              |               |              |                |                        |
| 5        |          102 | 11.333333     |           73 |              6 |                      6 |
| 15       |           22 | 13.000000     |           22 |              1 |                      1 |
| 16       |           44 | 2.000000      |           15 |              1 |                      1 |
| 17       |          180 | 23.333333     |           53 |              6 |                      6 |
| 18       |           40 | 1.000000      |           40 |              1 |                      1 |
+----------+--------------+---------------+--------------+----------------+------------------------+

我想要做的是根据每个索引将 count_watched_yeterday 列从 df_two 合并到 df_one 。

我尝试过:

video_base = pd.merge(df_one, df_two['count_watched_yeterday'], how='left', on=[df_one.index, df_two.index])

但是我收到了这个错误:ValueError:具有多个元素的数组的真值不明确。使用a.any()或a.all()

Answer 1

其实我觉得这里最简单的就是直接赋值:

In [13]:    
df['count_watched_yesterday'] = df1['count_watched_yeterday']
df['count_watched_yesterday']

Out[13]:
video_id
5      6
10   NaN
15     1
22   NaN
Name: count_watched_yesterday, dtype: float64

这是有效的，因为它将在索引值上对齐，如果没有匹配的值，则将分配 NaN 作为值