#!/usr/bin/python3

-- coding: utf-8 --

“”"
通过datetime和dateutil进行常用日期的获取
如：
今年，去年，明年
当前季度
本月，上月，去年同期，今年一月
今天，昨天，明天，
本周、本月、本季度、本年第一天，
本周、本月、本季度、本年最后一天
“”"

import datetime

获取常用特定日期（如去年/季度/当月/本周/首日/）

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关于年（今年，去年，明年）

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今年

today = datetime.date.today() # 都是基于today, 此时为’2019-02-22’，下同
today.year # out: 2019

去年

today = datetime.date.today()
today.year-1 # out : 2018

明年

today = datetime.date.today()
today.year+1 # out : 2020

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关于季度(当前季度)

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today = datetime.date.today()
quarter = (today.month-1) // 3 + 1
‘{}Q{}’.format(today.year, quarter) # out: ‘2019Q1’

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关于月(本月，上月，当年1月，去年同月)

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本月(月份)

today = datetime.date.today()
today.month # out: 2

本月(年月)

today = datetime.date.today()
datetime.datetime.strftime(today, “%Y-%m”) # out: ‘2019-02’

上月

today = datetime.date.today()
last_month = today + datetime.timedelta(days=-today.day)

last_month.month # 月份，out: 1

datetime.datetime.strftime(last_month,"%Y-%m") # out: ‘2019-01’

上N个月

from dateutil.relativedelta import relativedelta # 需要引入新的包
today = datetime.date.today()
last_2_month = today + relativedelta(months=-2) # 上两个月，上N个月参数为(months=-N)
datetime.datetime.strftime(last_2_month, “%Y-%m”) # out: ‘2018-12’

当年1月

today = datetime.date.today()
str(today.year) +’-01’ # out: ‘2019-01’

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关于天

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今天(天数)

today = datetime.date.today()
today.day

今天（日期）

today.isoformat() # out: ‘2019-02-22’

昨天

today = datetime.date.today()
yesterday = today + datetime.timedelta(days=-1)
yesterday.isoformat() # out: ‘2019-02-21’

明天

today = datetime.date.today()
yesterday = today + datetime.timedelta(days=1)
yesterday.isoformat() # out: ‘2019-02-23’

本周第一天

today = datetime.date.today()
week_start_day = today - datetime.timedelta(days=today.weekday())
week_start_day.isoformat() # ‘2019-02-18’，周一

本周最后一天

today = datetime.date.today()
week_end_day = today + datetime.timedelta(days=6-today.weekday())
week_end_day.isoformat() # ‘2019-02-24’，周天

本月第一天

today = datetime.date.today()
month_start_day = today - datetime.timedelta(days=today.day-1)
month_start_day.isoformat() # ‘2019-02-01’，当月第一天

本月最后一天

from dateutil.relativedelta import relativedelta # 引入新的包
today = datetime.date.today()

必须先置为首日，直接用relativedelta(months=1,days=-today.day+1)会有错误结果

month_end_day = (today + datetime.timedelta(days=-today.day+1)) + relativedelta(months=1,days=-1)
month_end_day.isoformat() # ‘2019-02-28’，当月最后一天

本季度第一天

today = datetime.date.today()
quarter_start_day = datetime.date(today.year,today.month - (today.month - 1) % 3, 1)
quarter_start_day.isoformat() # ‘2019-01-01’ ，本季度第一天

本季度最后一天

from dateutil.relativedelta import relativedelta # 引入新的包
today = datetime.date.today()
quarter_end_day = datetime.date(today.year,today.month - (today.month - 1) % 3 +2, 1) + relativedelta(months=1,days=-1)
quarter_end_day.isoformat() # ‘2019-03-31’ ，本季度最后一天

本年第一天

today = datetime.date.today()
year_start_day = datetime.date(today.year, 1, 1)
year_start_day.isoformat() # ‘2019-01-01’ ，本年第一天

本年最后一天

today = datetime.date.today()
year_end_day = datetime.date(today.year+1, 1, 1) - datetime.timedelta(days=1)
year_end_day.isoformat() # ‘2019-12-31’ ，本年最后一天