python - 减去熊猫中的日期时间
问题描述
我有数据框是这个
In[1]: df1
Out[1]
Loan Date Negotiation
2019-03-31
2019-03-31
2019-03-31
as Loan Date Negotiation datetime64[ns]
所以我想让函数从中减去 2 天。如果一个月的最后一天是星期天,我会从中减去 2 天。
从上面的数据框中,2019-03-31 是星期日,
我试过但失败了,这是
def subtractingDate(dateTime):
dateTimestamp = pd.Timestamp(dateTime)
newDate = dateTimestamp - pd.Timedelta("2 days")
return newDate
dfMARET.loc[dfMARET["Loan Date Negotiation"].dt.dayofweek == 6, "New Date"] = subtractingDate(dfMARET["Loan Date Negotiation"])
*note: 6 is for sunday
So the error is
TypeError Traceback (most recent call last)
<ipython-input-9-cc2a3348e6ce> in <module>
16 # a = subtractingDate(dfMARET["Loan Date Negotiation"])
17 # a
---> 18 dfMARET.loc[dfMARET["Loan Date Negotiation"].dt.dayofweek == 6, "New Date"] = subtractingDate(dfMARET["Loan Date Negotiation"])
19 dfMARET
20
<ipython-input-9-cc2a3348e6ce> in subtractingDate(dateTime)
10
11 def subtractingDate(dateTime):
---> 12 dateTimestamp = pd.Timestamp(dateTime)
13 newDate = dateTimestamp - pd.Timedelta(days = 2)
14 return newDate
pandas\_libs\tslibs\timestamps.pyx in pandas._libs.tslibs.timestamps.Timestamp.__new__()
pandas\_libs\tslibs\conversion.pyx in pandas._libs.tslibs.conversion.convert_to_tsobject()```
所以我的期望是
Loan Date Negotiation
2019-03-29
2019-03-29
2019-03-29
大熊猫的解决方案?
谢谢
解决方案
如果需要先将 datetime64 转换为 Timestamp,可以使用:
df['Date'] = [pd.Timestamp(x) for x in df['Date']]
并使用timedelta()
:
from datetime import datetime, timedelta
dt = pd.Timestamp(2019,3,31)
new_dt = dt-timedelta(days=2)
new_dt
> datetime.datetime(2019, 3, 29, 0, 0)
new_dt.strftime('%Y-%m-%d')
> '2019-03-29'
或在整个列Date
上:
df['New_Date'] = df['Date']-timedelta(days=2)
编辑:完整示例:
import numpy as np
from datetime import datetime, timedelta
df1 = pd.DataFrame([[np.datetime64(datetime(2019, 3, 31))],
[np.datetime64(datetime(2019, 3, 27))],
[np.datetime64(datetime(2019, 3, 24))]],
columns=['Loan Date Negotiation'])
df1
df1['Loan Date Negotiation'].dtype
> dtype('<M8[ns]')
M8[ns]
是 的特定类型datetime64[ns]
,因此进一步处理应该没有区别。
如果您只想在这一天是星期天的情况下减去两天,您可以使用np.where()
:
df1['New_Date'] = np.where(df1['Loan Date Negotiation'].dt.dayofweek==6,
df1['Loan Date Negotiation']-timedelta(days=2),
df1['Loan Date Negotiation'])
索引 0 和 2 的日期是星期天,减去了 2 天。未触及索引 1 处的日期。
通过对每个时间戳的列表理解进行替代
df1['New_Date'] = [x-timedelta(days=2) if x.weekday()==6 else x for x in df1['Loan Date Negotiation']]