python - 熊猫，按日期索引

Question

我在熊猫中有以下数据框

1   2015_04_19_00_00_00
2   2015_04_19_01_00_00
3   2015_04_19_02_00_00
4   2015_04_19_03_00_00
5   2015_04_19_04_00_00
6   2015_04_19_05_00_00
7   2015_04_19_06_00_00
8   2020_06_10_00_00_00
9   2020_06_10_01_00_00
10  2020_06_10_02_00_00
11  2020_06_10_03_00_00
12  2020_06_10_04_00_00
13  2020_06_10_05_00_00
14  2030_04_15_01_00_00
15  2030_04_15_02_00_00
16  2030_04_15_10_00_00
17  2030_04_15_11_00_00
18  2040_05_29_01_00_00
19  2040_05_29_02_00_00
20  2040_05_29_03_00_00
21  2040_05_29_04_00_00
22  2040_05_29_05_00_00
23  2040_05_29_06_00_00
24  2040_05_29_07_00_00
25  2040_05_29_08_00_00

如何查询年份变化的索引？

最终结果应该类似于

2015    1
2020    8
2030    14
2040    18

标签： pythonpandas

Answer 1

这是一种方法

In [148]: s = df.time_col.str.split('_').str[0]

In [149]: idx = s[s.ne(s.shift())]

In [150]: idx
Out[150]:
1     2015
8     2020
14    2030
18    2040
Name: time, dtype: object

In [151]: pd.Series(idx.index, idx.values)
Out[151]:
2015     1
2020     8
2030    14
2040    18
dtype: int64