如何索引python中的日期列

Question

我在python数据框中有一个日期列。我想通过订购日期来索引这些。这是python中的可能吗？

date     indexed
2007-02-21  3
2007-02-18  1
2007-02-24  5
2007-02-18  1
2007-02-23  4
2007-02-20  2
2007-02-23  4

我正在寻找索引，但我想我正在使用错误的术语来检查。请指导。

修改

实际上我想用等效的索引号替换日期。

Answer 1

您要查找的是按日期排序的值_

df = pd.DataFrame(["2007-02-21","2007-02-18","2007-02-24","2007-02-18","2007-02-23","2007-02-20","2007-02-23"],columns=["date"])

df.sort_values("date", axis=0)

Answer 2

您希望使用pd.factorize()方法的IIUC：

In [190]: df['new'] = pd.factorize(df['date'], sort=True)[0] + 1

In [191]: df
Out[191]:
        date  indexed  new
0 2007-02-21        3    3
1 2007-02-18        1    1
2 2007-02-24        5    5
3 2007-02-18        1    1
4 2007-02-23        4    4
5 2007-02-20        2    2
6 2007-02-23        4    4

PS pd.factorize()从0开始计算，因此我已添加1以满足您的预期结果

Answer 3

使用pandas.DataFrame.sort_index

import pandas as pd

df = pd.DataFrame(['2007-02-21','2007-02-18','2007-02-24','2007-02-18','2007-
02-23', '2007-02-20' , '2007-02-23'], index=[3, 1, 5, 1, 4,2,4], columns=
['Date'])

print df
         Date
3  2007-02-21
1  2007-02-18
5  2007-02-24
1  2007-02-18
4  2007-02-23
2  2007-02-20
4  2007-02-23


df2 = df.sort_index(axis=0)
print(df2)

         Date
1  2007-02-18
1  2007-02-18
2  2007-02-20
3  2007-02-21
4  2007-02-23
4  2007-02-23
5  2007-02-24