python 获取本周 ，上周，本月，上月，本季，上季，今年， 去年的第一天和最后一天

import datetime
from datetime import timedelta

now = datetime.datetime.now()

# 获取当前月的天数

month = 2
days = (datetime.date(2022, month + 1, 1) - datetime.timedelta(days=1)).day

#今天
today = now

#昨天
yesterday = now - timedelta(days=1)

#明天
tomorrow = now + timedelta(days=1)<br><br>#当前季度

#本周第一天和最后一天
this_week_start = now - timedelta(days=now.weekday())
this_week_end = now + timedelta(days=6-now.weekday())

#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)

#本月第一天和最后一天

this_month_start = datetime.datetime(year, month, 1)
if month == 12:
    this_month_end = datetime.datetime(year + 1, 1, 1) - timedelta(days=1)
else:
    this_month_end = datetime.datetime(year, month + 1, 1) - timedelta(days=1)

#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) 

#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 + 3, 1) - timedelta(days=1) 

#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) 

#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) 

#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)