import datetime
 
def getdate():
    # 获取前一天和前两天的时间
    pre2day= datetime.datetime.today().date() - datetime.timedelta(days=2)
    pre1date= datetime.datetime.today().date() - datetime.timedelta(days=1)
    print(pre2day, "=====", pre1date)
 
 
def get_offset_date(offset_day):
    # 获取前N天
    today = datetime.datetime.now()
    # 计算偏移量
    offset = datetime.timedelta(days=-offset_day)
    # 获取想要的日期的时间
    re_date = (today + offset).strftime('%Y-%m-%d')
    return re_date

    
def get_before_week_days(weeks=1):
    #获取前一周的所有日期(weeks=1)，获取前N周的所有日期(weeks=N)
    week = datetime.datetime.now().weekday()
    days_list = []
    start = 7 * weeks +  week
    end = week
    # 0,1,2,3,4,5,6,分别对应周一到周日  
    for index in range(start, end, -1):
        day =get_offset_date(index) 
        print(day)


if __name__ == '__main__':
   getdate()

import datetime

from datetime import timedelta

# 获取今天日期： #返回datetime格式：eg：2021-12-07 13:40:20.65623

now = datetime.datetime.now()

# 返回datetime格式：eg：2019-12-07

now = datetime.datetime.now().date()

now = datetime.date.today()

# 获取昨天日期：

yesterday = now - timedelta(days=1)

# 获取明天日期：

tomorrow = now + timedelta(days=1)

# 获取本周第一天和最后一天：

# 判断是周几
week_day = datetime.datetime.now().weekday()
    
this_week_start = now - timedelta(days=now.weekday())

this_week_end = now + timedelta(days=6-now.weekday())

# 获取上周第一天和最后一天：

last_week_start = now - timedelta(days=now.weekday()+7)

last_week_end = now - timedelta(days=now.weekday()+1)

# 获取本月第一天和最后一天：

this_month_start = datetime.datetime(now.year, now.month, 1)

this_month_end = datetime.datetime(now.year, now.month, calendar.monthrange(now.year, now.month)[1])

"""

calendar.monthrange(year,month) ：一个是当前的年份，另外一个是当前的月份

写法可以是：calendar.monthrange(now.year,now.month)

返回两个整数。

第一个值为该月第一天所在的星期几，对应的数字。0 - 6==>0（星期一）到6（星期日）

第二个值为该月一共几天。

"""

# 获取上月第一天和最后一天 ：

last_month_end = this_month_start - timedelta(days=1)

last_month_start = datetime.datetime(last_month_end.year, last_month_end.month, 1)

# 获取本季第一天和最后一天：

month = (now.month - 1) - (now.month - 1) % 3 + 1

this_quarter_start = datetime.datetime(now.year, month, 1)

this_quarter_end = datetime.datetime(now.year, month, calendar.monthrange(now.year, now.month)[1])

# 获取上季第一天和最后一天：

last_quarter_end = this_quarter_start - timedelta(days=1)

last_quarter_start = datetime.datetime(last_quarter_end.year, last_quarter_end.month - 2, 1)

# 获取本年第一天和最后一天：

this_year_start = datetime.datetime(now.year, 1, 1)

this_year_end = datetime.datetime(now.year + 1, 1, 1) - timedelta(days=1)

#  获取去年第一天和最后一天：

last_year_end = this_year_start - timedelta(days=1)

last_year_start = datetime.datetime(last_year_end.year, 1, 1)


def first_day_of_month():
    """
    获取当月第一天日期
    """
    now = datetime.datetime.now()
    return datetime.datetime(now.year, now.month, 1)


# 当月第1天
first_month_day = first_day_of_month().day


month_day = datetime.datetime.today().day
# 判断是当月第几天
if month_day == first_month_day:
    pass