我正在使用datetime Python模块。我希望从当前日期计算6个月的日期。有人能帮我一下吗?

我想从当前日期生成一个6个月后的日期的原因是为了生成一个回顾日期。如果用户在系统中输入数据,系统将有从输入数据之日起6个月的审查日期。


当前回答

只需使用timetuple方法提取月份,添加您的月份并构建一个新的dateobject。如果有一个已经存在的方法,我不知道它。

import datetime

def in_the_future(months=1):
    year, month, day = datetime.date.today().timetuple()[:3]
    new_month = month + months
    return datetime.date(year + (new_month / 12), (new_month % 12) or 12, day)

这个API有点笨拙,但可以作为示例使用。这显然也不适用于像2008-01-31 + 1个月这样的极端情况。:)

其他回答

另一种解决方案:计算下个月的天数总和,并将结果添加到当前日期。

import calendar
import datetime

def date_from_now(months):
    today = datetime.datetime.today()

    month = today.month
    year = today.year
    sum_days = 0

    for i in range(int(months)):
        month += 1

        if month == 13:
            month = 1
            year += 1

        sum_days += calendar.monthrange(year, month)[1]

    return datetime.date.today() + datetime.timedelta(sum_days)

print(date_from_now(12)) # if to day is 2017-01-01, output: 2019-01-01 

下面是一个示例,它允许用户决定如何返回一个日期,其中一天大于一个月中的天数。

def add_months(date, months, endOfMonthBehaviour='RoundUp'):
    assert endOfMonthBehaviour in ['RoundDown', 'RoundIn', 'RoundOut', 'RoundUp'], \
        'Unknown end of month behaviour'
    year = date.year + (date.month + months - 1) / 12
    month = (date.month + months - 1) % 12 + 1
    day = date.day
    last = monthrange(year, month)[1]
    if day > last:
        if endOfMonthBehaviour == 'RoundDown' or \
            endOfMonthBehaviour == 'RoundOut' and months < 0 or \
            endOfMonthBehaviour == 'RoundIn' and months > 0:
            day = last
        elif endOfMonthBehaviour == 'RoundUp' or \
            endOfMonthBehaviour == 'RoundOut' and months > 0 or \
            endOfMonthBehaviour == 'RoundIn' and months < 0:
            # we don't need to worry about incrementing the year
            # because there will never be a day in December > 31
            month += 1
            day = 1
    return datetime.date(year, month, day)


>>> from calendar import monthrange
>>> import datetime
>>> add_months(datetime.datetime(2016, 1, 31), 1)
datetime.date(2016, 3, 1)
>>> add_months(datetime.datetime(2016, 1, 31), -2)
datetime.date(2015, 12, 1)
>>> add_months(datetime.datetime(2016, 1, 31), -2, 'RoundDown')
datetime.date(2015, 11, 30)

我找不到这个问题的确切解决方案,所以我将发布我的解决方案,以防使用标准日历和datetime库可能有任何帮助。这适用于添加和减去月份,并考虑月末滚动和最后一个月比第一个月天数少的情况。如果你正在寻找更复杂的操作,我还有一个更通用的解决方案,它添加了定期间隔(天,月,年,季度,学期等),如:“1m”,“-9m”,“-1.5y”,“-3q”,“1s”等。

from datetime import datetime
from calendar import monthrange
def date_bump_months(start_date, months):
    """
    bumps months back and forth. 
    --> if initial date is end-of-month, i will move to corresponding month-end
    --> ir inital date.day is greater than end of month of final date, it casts it to momth-end
    """
    signbit = -1 if months < 0 else 1
    d_year, d_month = divmod(abs(months),12)    
    end_year = start_date.year + d_year*signbit 
    end_month = 0
    if signbit ==-1:            
        if d_month < start_date.month:
            end_month = start_date.month - d_month
        else:
            end_year -=1
            end_month = 12 - (d_month - start_date.month)
    else:
        end_month +=start_date.month
        if end_month  > 12:
            end_year +=1
            end_month -=12
    # check if we are running end-of-month dates
    eom_run = monthrange(start_date.year, start_date.month)[1]==start_date.day
    eom_month = monthrange((end_year), (end_month))[1]
    if eom_run:
        end_day = eom_month 
    else:
        end_day = min(start_date.day, eom_month )    
    return date(end_year, end_month, end_day)

我插话晚了,但是

查看肯雷茨玛雅模块,

https://github.com/kennethreitz/maya

像这样的方法可能会对你有帮助,只需将小时=1改为天=1或年=1

>>> from maya import MayaInterval

# Create an event that is one hour long, starting now.
>>> event_start = maya.now()
>>> event_end = event_start.add(hours=1)

>>> event = MayaInterval(start=event_start, end=event_end)

获得x个月之后或之前的下一个日期的一般函数。

from datetime import date

def after_month(given_date, month):
    yyyy = int(((given_date.year * 12 + given_date.month) + month)/12)
    mm = int(((given_date.year * 12 + given_date.month) + month)%12)

    if mm == 0:
        yyyy -= 1
        mm = 12
    return given_date.replace(year=yyyy, month=mm)


if __name__ == "__main__":
    today = date.today()
    print(today)

    for mm in [-12, -1, 0, 1, 2, 12, 20 ]:
        next_date = after_month(today, mm)
        print(next_date)