Python 从周数获取日期
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Get date from week number
提问by Ali SAID OMAR
Please what's wrong with my code:
请问我的代码有什么问题：
import datetime
d = "2013-W26"
r = datetime.datetime.strptime(d, "%Y-W%W")
print(r)
Display "2013-01-01 00:00:00", Thanks.
显示“2013-01-01 00:00:00”，谢谢。
采纳答案by Martijn Pieters
A week number is not enough to generate a date; you need a day of the week as well. Add a default:
周数不足以生成日期；你也需要一周中的一天。添加默认值：
import datetime
d = "2013-W26"
r = datetime.datetime.strptime(d + '-1', "%Y-W%W-%w")
print(r)
The -1and -%wpattern tells the parser to pick the Monday in that week. This outputs:
在-1和-%w模式告诉解析器挑周一在那一周。这输出：
2013-07-01 00:00:00
%Wuses Monday as the first day of the week. While you can pick your own weekday, you may get unexpected results if you deviate from that.
%W使用星期一作为一周的第一天。虽然您可以选择自己的工作日，但如果您偏离了它，您可能会得到意想不到的结果。
See the strftime()and strptime()behavioursection in the documentation, footnote 4:
请参阅文档中的strftime()和strptime()行为部分，脚注 4：
When used with the
strptime()method,%Uand%Ware only used in calculations when the day of the week and the year are specified.
当与使用
strptime()方法，%U并%W指定了一周，一年中的一天，在计算仅使用。
Note, if your week number is a ISO week date, you'll want to use %G-W%V-%uinstead! Those directives require Python 3.6 or newer.
请注意，如果您的周数是ISO 周日期，则您需要%G-W%V-%u改用！这些指令需要 Python 3.6 或更新版本。
回答by Ron
Here's a handy functionincluding the issue with zero-week.
这是一个方便的功能，包括零周问题。
回答by Senthilkumar C
import datetime
res = datetime.datetime.strptime("2018 W30 w1", "%Y %W w%w")
print res
Adding of 1 as week day will yield exact current week start. Adding of timedelta(days=6) will gives you the week end.
添加 1 作为工作日将产生准确的当前周开始。添加 timedelta(days=6) 将为您提供周末。
datetime.datetime(2018, 7, 23)
回答by Luka Kikelj
To complete the other answers - if you are using ISOweek numbers, this string is appropriate (to get the Monday of a given ISO week number):
要完成其他答案 - 如果您使用ISO周数，则此字符串是合适的（获取给定 ISO 周数的星期一）：
import datetime
d = '2013-W26'
r = datetime.datetime.strptime(d + '-1', '%G-W%V-%u')
print(r)
%G, %V, %uare ISO equivalents of %Y, %W, %w, so this outputs:
%G，%V，%u是ISO当量%Y，%W，%w，所以这个输出：
2013-06-24 00:00:00
Availabe in Python 3.6+; from docs.
在 Python 3.6+ 中可用；来自文档。
回答by dimosbele
In case you have the yearly number of week, just add the number of weeks to the first day of the year.
如果您有每年的周数，只需将周数添加到一年的第一天。
>>> import datetime
>>> from dateutil.relativedelta import relativedelta
>>> week = 40
>>> year = 2019
>>> date = datetime.date(year,1,1)+relativedelta(weeks=+week)
>>> date
datetime.date(2019, 10, 8)
回答by Jens W. Klein
In Python 3.8 there is the handy datetime.date.fromisocalendar:
在 Python 3.8 中有一个方便的datetime.date.fromisocalendar：
>>> from datetime import date
>>> date.fromisocalendar(2020, 1, 1) # (year, week, day of week)
datetime.date(2019, 12, 30, 0, 0)
In older Python versions (3.7-) the calculation can use the information from datetime.date.isocalendarto figure out the week ISO8601 compliant weeks:
在较旧的 Python 版本 (3.7-) 中，计算可以使用信息datetime.date.isocalendar来计算 符合 ISO8601 的周数：
from datetime import date, timedelta
def monday_of_calenderweek(year, week):
first = date(year, 1, 1)
base = 1 if first.isocalendar()[1] == 1 else 8
return first + timedelta(days=base - first.isocalendar()[2] + 7 * (week - 1))
Both works also with datetime.datetime.
两者都适用于datetime.datetime.
