从Python中的ISO周编号获取日期 [英] Get date from ISO week number in Python

问题描述

可能重复:
找到日期时间倒数的最佳方法是什么.isocalendar()?

Possible Duplicate:
What’s the best way to find the inverse of datetime.isocalendar()?

我有一个ISO 8601年和周号，我需要将其转换为该周第一天的日期(星期一).我该怎么办?

I have an ISO 8601 year and week number, and I need to translate this to the date of the first day in that week (Monday). How can I do this?

datetime.strptime()同时使用%W和%U指令，但均未遵循

datetime.strptime() takes both a %W and a %U directive, but neither adheres to the ISO 8601 weekday rules that datetime.isocalendar() use.

更新: Python 3.6 支持libc中也存在的%G，%V和%u指令，从而允许这种单行代码:

Update: Python 3.6 supports the %G, %V and %u directives also present in libc, allowing this one-liner:

>>> datetime.strptime('2011 22 1', '%G %V %u')
datetime.datetime(2011, 5, 30, 0, 0)

更新2 : Python 3.8 添加了fromisocalendar()方法，该方法更加直观:

Update 2: Python 3.8 added the fromisocalendar() method, which is even more intuitive:

>>> datetime.fromisocalendar(2011, 22, 1)
datetime.datetime(2011, 5, 30, 0, 0)

推荐答案

％W将第一个星期一设为第1周，但ISO将第1周定义为包含1月4日.所以结果来自

%W takes the first Monday to be in week 1 but ISO defines week 1 to contain 4 January. So the result from

datetime.strptime('2011221', '%Y%W%w')

如果在不同的一周的第一个星期一和1月4日，

关闭. 如果1月4日是星期五，星期六或星期日，则后者是这种情况. 因此，以下方法应该起作用:

is off by one iff the first Monday and 4 January are in different weeks. The latter is the case if 4 January is a Friday, Saturday or Sunday. So the following should work:

from datetime import datetime, timedelta, date
def tofirstdayinisoweek(year, week):
    ret = datetime.strptime('%04d-%02d-1' % (year, week), '%Y-%W-%w')
    if date(year, 1, 4).isoweekday() > 4:
        ret -= timedelta(days=7)
    return ret

这篇关于从Python中的ISO周编号获取日期的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！