Python Pandas —在两个数据框中映射值

Question

我有两个数据df1和df2 。

我试图找出执行映射的最佳方法，即对于df1中的每一行，我想在df2搜索匹配项（ id ， time_by_hour ），然后将df2的相应值填回到df1 。

下面是df1_final ，我希望它最终看起来是。

先感谢您！

df1
Out[100]: 
  id             time_by_min        time_by_hour  value
0  a 2017-06-30 01:25:00.000 2017-06-30 02:00:00    NaN
1  a 2017-06-30 01:36:32.308 2017-06-30 02:00:00    NaN
2  a 2017-06-30 02:25:00.000 2017-06-30 03:00:00    NaN
3  a 2017-06-30 02:36:32.308 2017-06-30 03:00:00    NaN
4  b 2017-06-30 01:25:00.000 2017-06-30 02:00:00    NaN
5  b 2017-06-30 01:36:32.308 2017-06-30 02:00:00    NaN
6  b 2017-06-30 02:25:00.000 2017-06-30 03:00:00    NaN

df2
Out[101]: 
  id        time_by_hour  value
0  a 2017-06-30 02:00:00    100
1  a 2017-06-30 03:00:00    200
2  b 2017-06-30 02:00:00    150
3  b 2017-06-30 03:00:00     30
4  c 2017-06-30 02:00:00     80
5  c 2017-06-30 03:00:00    900

df1_final
Out[102]: 
  id             time_by_min        time_by_hour  value
0  a 2017-06-30 01:25:00.000 2017-06-30 02:00:00    100
1  a 2017-06-30 01:36:32.308 2017-06-30 02:00:00    100
2  a 2017-06-30 02:25:00.000 2017-06-30 03:00:00    200
3  a 2017-06-30 02:36:32.308 2017-06-30 03:00:00    200
4  b 2017-06-30 01:25:00.000 2017-06-30 02:00:00    150
5  b 2017-06-30 01:36:32.308 2017-06-30 02:00:00    150
6  b 2017-06-30 02:25:00.000 2017-06-30 03:00:00     30

Answer 1

你可以看一下merge

df1['value']=df1[['time_by_hour','id']].merge(df2,how='left').value