如何在基于两个数据框之间的多个条件的数据框中获取新列？答案

【问题标题】：How to get new column in dataframe that is based on multiple conditions between two dataframes?如何在基于两个数据框之间的多个条件的数据框中获取新列？
【发布时间】：2022-12-14 10:33:03
【问题描述】：

我有两个数据框，我希望在 DF1 中获得一个列，该列将具有“当前日期”列的值加上与 DF2 中的相关状态和技术相关的天数。例如，在下面的“新日期”列中的第一个值是 18/03/2022 + 1095 天，因为它正在检查技术是否 = 风和状态 = 施工。

东风1

Current Date	Technology	Status	New Date DESIRED FROM CODE
18/03/2022	Wind	Construction	16/12/2022
15/02/2022	Solar	Construction	15/11/2022
24/01/2022	Battery	Application approved	24/10/2022
23/09/2020	Wind	Application approved	24/03/2023
18/11/2021	Solar	Application submitted	18/11/2023
25/06/2020	Solar	Application approved	25/03/2021
27/02/2020	Wind	Application submitted	25/02/2025
10/03/2022	Battery	Application submitted	09/03/2024

东风2

Technology	Application submitted	Application approved	Construction
Battery	730	273.75	273.75
Solar Photovoltaics	730	273.75	273.75
Wind	1825	912.5	1095

【问题讨论】：

标签： python pandas dataframe

【解决方案1】：

利用：

df2 = (df2.melt('Technology', var_name='Status')
          .assign(value = lambda x: pd.to_timedelta(x['value'].astype(int), unit='d')))
print (df2)
            Technology                 Status     value
0              Battery  Application submitted  730 days
1  Solar Photovoltaics  Application submitted  730 days
2                 Wind  Application submitted 1825 days
3              Battery   Application approved  273 days
4  Solar Photovoltaics   Application approved  273 days
5                 Wind   Application approved  912 days
6              Battery           Construction  273 days
7  Solar Photovoltaics           Construction  273 days
8                 Wind           Construction 1095 days

【讨论】：