DataFrame.set_index('column') 將列設置為行索引
In [77]: df2[:7]
Out[77]:
time key value
0 2017-05-20 00:00:00 a 0.0
1 2017-05-20 00:00:00 b 1.0
2 2017-05-20 00:00:00 c 2.0
3 2017-05-20 00:01:00 a 3.0
4 2017-05-20 00:01:00 b 4.0
5 2017-05-20 00:01:00 c 5.0
6 2017-05-20 00:02:00 a 6.0
In [79]: df2.set_index('key')[:7]
Out[79]:
time value
key
a 2017-05-20 00:00:00 0.0
b 2017-05-20 00:00:00 1.0
c 2017-05-20 00:00:00 2.0
a 2017-05-20 00:01:00 3.0
b 2017-05-20 00:01:00 4.0
c 2017-05-20 00:01:00 5.0
a 2017-05-20 00:02:00 6.0