Python：如何从列计算差异btw当前年份和年份？

Question

我有一个专栏＆＃34; DateBecameRep_Year＆＃34;其中只包含年份值（即1974年，1999年等）。我想在我的数据框架中创建一个新列，用于计算＆＃34; DateBecameRep_Year＆＃34;中的当前年份和年份之间的差异。领域。

以下是我尝试使用的代码：

df_DD['DateBecameRep_Year'] = pd.to_datetime(df_DD['DateBecameRep_Year'])

df_DD['Current Year'] = datetime.now().year
df_DD['Current Year'] = pd.to_datetime(df_DD['Current Year'])

df_DD['Years_Since_BecameRep'] = df_DD['Current Year'] - df_DD['DateBecameRep_Year']  
df_DD['Years_Since_BecameRep'] = df_DD['Years_Since_BecameRep'] / np.timedelta64(1, 'Y')

df_DD['Years_Since_BecameRep'].head()

这是我得到的输出看起来很奇怪：

我的假设是，这与以下内容有关：

非常感谢任何帮助！

Answer 1

如果您只想获得不同的年份数，您可以简单地使用减法，无需转换为日期时间。

import pandas as pd
import datetime
current_year = datetime.datetime.now().year #get current year
df_DD = pd.DataFrame.from_dict({"DateBecameRep_Year":[1999,2000,2015,1898,1788,1854]})
df_DD['Current Year'] = datetime.datetime.now().year
df_DD["Years_Since_BecameRep"] = df_DD['Current Year'] - df_DD['DateBecameRep_Year']  # substract to get the year delta

df_DD将是：

    DateBecameRep_Year  Current Year    Years_Since_BecameRep
0   1999                2017            18
1   2000                2017            17
2   2015                2017            2
3   1898                2017            119
4   1788                2017            229
5   1854                2017            163