dateutils rrule returns 相隔 2 个月的日期

Question

我是 Python 和 dateutil 模块的新手。我传递以下参数：

disclosure_start_date = resultsDict['fd_disclosure_start_date']
disclosure_end_date = datetime.datetime.now()
disclosure_dates = [dt for dt in rrule(MONTHLY, dtstart=disclosure_start_date, until=disclosure_end_date)]

这里disclosure_start_date = 2012-10-31 00:00:00转换为datetime是datetime.datetime(2012, 10, 31, 0, 0)

截止日期为现在。

当我使用：

disclosure_dates = [dt for dt in rrule(MONTHLY, dtstart=disclosure_start_date, until=disclosure_end_date)]

我每隔一个月或相隔 2 个月获取日期。结果是：

>>> list(disclosure_dates)
[datetime.datetime(2012, 10, 31, 0, 0), 
 datetime.datetime(2012, 12, 31, 0, 0), 
 datetime.datetime(2013, 1, 31, 0, 0), 
 datetime.datetime(2013, 3, 31, 0, 0), 
 datetime.datetime(2013, 5, 31, 0, 0), 
 datetime.datetime(2013, 7, 31, 0, 0), 
 datetime.datetime(2013, 8, 31, 0, 0), 
 datetime.datetime(2013, 10, 31, 0, 0), 
 datetime.datetime(2013, 12, 31, 0, 0), 
 datetime.datetime(2014, 1, 31, 0, 0), 
 datetime.datetime(2014, 3, 31, 0, 0), 
 datetime.datetime(2014, 5, 31, 0, 0), 
 datetime.datetime(2014, 7, 31, 0, 0), 
 datetime.datetime(2014, 8, 31, 0, 0), 
 datetime.datetime(2014, 10, 31, 0, 0), 
 datetime.datetime(2014, 12, 31, 0, 0), 
 datetime.datetime(2015, 1, 31, 0, 0), 
 datetime.datetime(2015, 3, 31, 0, 0), 
 datetime.datetime(2015, 5, 31, 0, 0), 
 datetime.datetime(2015, 7, 31, 0, 0), 
 datetime.datetime(2015, 8, 31, 0, 0), 
 datetime.datetime(2015, 10, 31, 0, 0), 
 datetime.datetime(2015, 12, 31, 0, 0), 
 datetime.datetime(2016, 1, 31, 0, 0), 
 datetime.datetime(2016, 3, 31, 0, 0), 
 datetime.datetime(2016, 5, 31, 0, 0)]

我不确定我做错了什么。有人可以指出这里的错误吗？

Answer 1

您遇到的问题是因为 datetime.datetime(2012, 10, 31, 0, 0) 是该月的 31 号，并非所有月份都有 31 号。由于 rrule 模块是 RFC 2445 的实现。根据 RFC 3.3.10：

Recurrence rules may generate recurrence instances with an invalid date (e.g., February 30) or nonexistent local time (e.g., 1:30 AM on a day where the local time is moved forward by an hour at 1:00 AM). Such recurrence instances MUST be ignored and MUST NOT be counted as part of the recurrence set.

由于您有一个生成每月 31 日的月度规则，它会跳过所有天数不超过 30 天的月份。您可以在 dateutil 中查看有关此问题的 this bug report。

如果你只想要一个月的最后一天，你应该使用 bymonthday=-1 参数：

from dateutil.rrule import rrule, MONTHLY
from datetime import datetime

disclosure_start_date = datetime(2012, 10, 31, 0, 0)

rr = rrule(freq=MONTHLY, dtstart=disclosure_start_date, bymonthday=-1)
# >>>rr.between(datetime(2013, 1, 1), datetime(2013, 5, 1))
# [datetime.datetime(2013, 1, 31, 0, 0),
#  datetime.datetime(2013, 2, 28, 0, 0),
#  datetime.datetime(2013, 3, 31, 0, 0),
#  datetime.datetime(2013, 4, 30, 0, 0)]

不幸的是，我不认为有一种符合 RFC 标准的方法来生成一个简单的 RRULE，当且仅当它是必要的时候（例如，你对一月做什么） 30 日 - 您需要为 2 月回退，但您不想使用 bymonthday=-2，因为那样会给您 2 月 27 日等）。

或者，对于像这样的简单月度规则，更好的选择可能是只使用 relativedelta，会回落到月末：

from dateutil.relativedelta import relativedelta
from datetime import datetime

def disclosure_dates(dtstart, rd, dtend=None):
    ii = 0
    while True:
        cdate = dtstart + ii*rd
        ii += 1

        yield cdate
        if dtend is not None and cdate >= dtend:
            break


dtstart = datetime(2013, 1, 31, 0, 0)
rd = relativedelta(months=1)
rr = disclosure_dates(dtstart, rd, dtend=datetime(2013, 5, 1))

# >>> list(rr)
# [datetime.datetime(2013, 1, 31, 0, 0),
#  datetime.datetime(2013, 2, 28, 0, 0),
#  datetime.datetime(2013, 3, 31, 0, 0),
#  datetime.datetime(2013, 4, 30, 0, 0),
#  datetime.datetime(2013, 5, 31, 0, 0)]

请注意，我专门使用了 cdate = dtstart + ii * rd，你 而不是 只想保留一个 "running tally"，因为这会将计数固定到最短的月份看过：

dt_base = datetime(2013, 1, 31)
dt = dt_base
for ii in range(5):
    cdt = dt_base + ii*rd
    print('{} | {}'.format(dt, cdt))
    dt += rd

结果：

2013-01-31 00:00:00 | 2013-01-31 00:00:00
2013-02-28 00:00:00 | 2013-02-28 00:00:00
2013-03-28 00:00:00 | 2013-03-31 00:00:00
2013-04-28 00:00:00 | 2013-04-30 00:00:00
2013-05-28 00:00:00 | 2013-05-31 00:00:00

Answer 2

"datetime.datetime(2022, 1, 3, 0, 0)"

dateutils rrule returns 相隔 2 个月的日期

dateutils rrule returns dates that 2 months apart

python

datetime

date

rrule

python-dateutil