“在仅使用天数时，'datetime.timedelta'和'dateutil.relativedelta.relativedelta'之间有什么差异？”

Question

当只使用天时，^{}（来自Python的标准库）和^{}之间有什么区别？

据我所知，timedelta仅支持天（和周），而relativedelta添加了对按年、月、周或天定义的期间的支持，以及对年、月或天定义的绝对值的支持。（记住，就这个问题而言，我不必担心小时、分钟或秒）

考虑到我只处理^{}对象，只对由天数定义的周期感兴趣，那么timedelta和relativedelta之间有什么区别？有什么区别吗？

from datetime import date, timedelta
from dateutil.relativedelta import relativedelta

i = -1  # This could have been any integer, positive or negative
someday = date.today()
# Is there any difference between these two lines?
otherday = someday + timedelta(days=i)
otherday = someday + relativedelta(days=i)

Answer 1

一个relativedelta比一个timedelta有更多的参数：

Definition:   relativedelta.relativedelta(self, dt1=None, dt2=None,
years=0, months=0, days=0, leapdays=0, weeks=0, hours=0, minutes=0,
seconds=0, microseconds=0, year=None, month=None, day=None,
weekday=None, yearday=None, nlyearday=None, hour=None, minute=None,
second=None, microsecond=None)

你可以用它来计算一个月内的最后一个星期五：

In [14]: import datetime as dt

In [15]: import dateutil.relativedelta as relativedelta

In [16]: today = dt.date.today()

In [17]: rd = relativedelta.relativedelta(day = 31, weekday = relativedelta.FR(-1))

In [18]: today+rd
Out[18]: datetime.date(2012, 9, 28)