@david-ragazzi和@mikedugas77的答案适用于正值months
,但是如果months <= -date.month
则不适用。这里有一个修改版,即使对于负月偏移量也应该有效:
import calendar
import datetime
def add_months(date, months):
months_count = date.year * 12 + date.month + months - 1
year = months_count // 12
month = months_count % 12 + 1
day = date.day
last_day_of_month = calendar.monthrange(year, month)[1]
if day > last_day_of_month:
day = last_day_of_month
new_date = datetime.date(year, month, day)
return new_date
使用今天的日期进行一些测试:
date = datetime.date(2020, 7, 30)
assert add_months(date, -12) == datetime.date(2019, 7, 30)
assert add_months(date, -11) == datetime.date(2019, 8, 30)
assert add_months(date, -10) == datetime.date(2019, 9, 30)
assert add_months(date, -9) == datetime.date(2019, 10, 30)
assert add_months(date, -8) == datetime.date(2019, 11, 30)
assert add_months(date, -7) == datetime.date(2019, 12, 30)
assert add_months(date, -6) == datetime.date(2020, 1, 30)
assert add_months(date, -5) == datetime.date(2020, 2, 29)
assert add_months(date, -4) == datetime.date(2020, 3, 30)
assert add_months(date, -3) == datetime.date(2020, 4, 30)
assert add_months(date, -2) == datetime.date(2020, 5, 30)
assert add_months(date, -1) == datetime.date(2020, 6, 30)
assert add_months(date, 0) == datetime.date(2020, 7, 30)
assert add_months(date, 1) == datetime.date(2020, 8, 30)
assert add_months(date, 2) == datetime.date(2020, 9, 30)
assert add_months(date, 3) == datetime.date(2020, 10, 30)
assert add_months(date, 4) == datetime.date(2020, 11, 30)
assert add_months(date, 5) == datetime.date(2020, 12, 30)
assert add_months(date, 6) == datetime.date(2021, 1, 30)
assert add_months(date, 7) == datetime.date(2021, 2, 28)
assert add_months(date, 8) == datetime.date(2021, 3, 30)
assert add_months(date, 9) == datetime.date(2021, 4, 30)
assert add_months(date, 10) == datetime.date(2021, 5, 30)
assert add_months(date, 11) == datetime.date(2021, 6, 30)
assert add_months(date, 12) == datetime.date(2021, 7, 30)