如何在 PANDAS/PYTHON 中的数据框中找到月份的最大可用日期

Question

假设我有一个数据框

date,ent_id,val
2021-03-23,109,61
2021-03-12,104,64
2021-03-31,101,61
2021-03-30,103,64
2021-04-01,111,32
2021-04-01,153,39
2021-04-30,101,51
2021-04-30,103,53
2021-05-12,101,28
2021-05-07,103,26
2021-05-05,171,47
2021-05-05,183,61
2021-06-06,131,45
2021-06-06,133,78
2021-06-30,101,23
2021-06-30,103,31

我想找出当月的maximum available date

我知道如何在 sql

中执行此操作

max(date) over (partition by date_part(year,date),date_part(month,date))

但我无法在 pandas 中找到任何逻辑，或者是否有针对此的任何内置函数

所以输出会像

date,ent_id,val,max_avl_d
2021-03-23,109,61,2021-03-31
2021-03-12,104,64,2021-03-31
2021-03-31,101,61,2021-03-31
2021-03-30,103,64,2021-03-31
2021-04-01,111,32,2021-04-30
2021-04-01,153,39,2021-04-30
2021-04-30,101,51,2021-04-30
2021-04-30,103,53,2021-04-30
2021-05-12,101,28,2021-05-12
2021-05-07,103,26,2021-05-12
2021-05-05,171,47,2021-05-12
2021-05-05,183,61,2021-05-12
2021-06-06,131,45,2021-06-30
2021-06-06,133,78,2021-06-30
2021-06-30,101,23,2021-06-30
2021-06-30,103,31,2021-06-30

Answer 1

这是一个您可以尝试的解决方案，

df['date'] = pd.to_datetime(df['date'], format='%Y-%m-%d')

df['max_date'] = (
    df.groupby([df['date'].dt.year, df['date'].dt.month])['date'].transform('max')
)

         date  ent_id  val   max_date
0  2021-03-23     109   61 2021-03-31
1  2021-03-12     104   64 2021-03-31
2  2021-03-31     101   61 2021-03-31
...

Answer 2

我们可以利用 to_period() 和 to_timestamp() 来获取所提供月份日期的最后日期。

df['max_avl_d'] =  df.date.dt.to_period('M').dt.to_timestamp('M')

输出：

    date    ent_id  val max_avl_d
0   2021-03-23  109 61  2021-03-31
1   2021-03-12  104 64  2021-03-31
2   2021-03-31  101 61  2021-03-31
3   2021-03-30  103 64  2021-03-31
4   2021-04-01  111 32  2021-04-30
5   2021-04-01  153 39  2021-04-30
6   2021-04-30  101 51  2021-04-30
7   2021-04-30  103 53  2021-04-30
8   2021-05-12  101 28  2021-05-31
9   2021-05-07  103 26  2021-05-31
10  2021-05-05  171 47  2021-05-31
11  2021-05-05  183 61  2021-05-31
12  2021-06-06  131 45  2021-06-30
13  2021-06-06  133 78  2021-06-30
14  2021-06-30  101 23  2021-06-30
15  2021-06-30  103 31  2021-06-30

如何在 PANDAS/PYTHON 中的数据框中找到月份的最大可用日期

how to find maximum available date of the month in dataframe in PANDAS/PYTHON

python

numpy

pandas

data-science