Question

我有一个如下所示的pd.dataframe：

key_value     date
value_01   2017-01-13
value_01   2018-02-17
value_01   2018-04-02
value_01   2018-05-13
value_01   2018-05-16  
value_02   2017-01-18
value_02   2018-03-13
value_02   2018-04-01
value_02   2018-05-16  
value_02   2018-05-22  
value_03   2018-01-13
value_03   2018-04-14

现在基于key_value，

我要删除日期列值在2018-04-01之前的所有行

我想要这样的最终输出：

 key_value     date
value_01   2018-04-02
value_01   2018-05-13
value_01   2018-05-16  
value_02   2018-04-01
value_02   2018-05-16  
value_02   2018-05-22  
value_03   2018-04-14

Answer 1

您可以只使用布尔索引来过滤数据框。这里没有分组操作。只记得先将系列转换为datetime。

df['date'] = pd.to_datetime(df['date'])

res = df[~(df['date'] < '2018-04-01')]

print(res)

   key_value       date
2   value_01 2018-04-02
3   value_01 2018-05-13
4   value_01 2018-05-16
7   value_02 2018-04-01
8   value_02 2018-05-16
9   value_02 2018-05-22
11  value_03 2018-04-14

Answer 2

也许这段代码不是最好的，但是即使您的日期没有排序，您的要求也可以做到。

import pandas as pd
from datetime import datetime

d = {'key_value': [1, 2, 3, 4, 5], 'date': ['2017-01-13', '2018-02-17','2018-04-02','2018-05-13','2018-05-16']}#create dataframe

date_string='2018-04-01'#date limit
date_to_drop=datetime.strptime(date_string, '%Y-%m-%d')# conmert my date to datetime
i=0
l=len(d['date'])#len of your set of date
while i<l:#loop on your set of date
    datetime_object = datetime.strptime(d['date'][i], '%Y-%m-%d')#convert the current date in datetime
    if datetime_object<date_to_drop:#if my current date is previous of the date limit I delete it from my dataframe
        d['date'].pop(i)#delete the date
        d['key_value'].pop(i)#delete the key_value
        l-=1#decrese the len of the date set of 1 seeing that I delete an element
    else:#if my current date is after of date limit I just pass to next iteration
        i+=1
df = pd.DataFrame(data=d)
print (df)

这是结果

         date  key_value
0  2018-04-02          3
1  2018-05-13          4
2  2018-05-16          5

Answer 3

有点晚了，但这是我的解决方案。尝试使用一些没有熊猫的pythonic东西。也许更容易阅读。

from datetime import datetime

data = {}
specificDate = datetime.strptime("2018-04-01", "%Y-%m-%d")

data.update({"value_01" : ["2017-01-13", "2018-02-17", "2018-04-02", "2018-05-13", "2018-05-16"]})
data.update({"value_02" : ["2017-01-18", "2018-03-13", "2018-04-01", "2018-05-16", "2018-05-22"]})
data.update({"value_03" : ["2018-01-13", "2018-04-14"]})

for key in data.keys():
    data.update({key : list(filter(lambda x: datetime.strptime(x, "%Y-%m-%d") >= specificDate ,data[key]))})

for key, value in data.items():
    print(key)
    for val in value:
        print("    " + val)

输出：

value_01
    2018-04-02
    2018-05-13
    2018-05-16
value_02
    2018-04-01
    2018-05-16
    2018-05-22
value_03
    2018-04-14

根据键值删除日期在要求的日期点之前的行

3 个答案: