如何在python中获得像我们使用的那样的yearWeek日期时间格式info.InvariantInfo.CalendarC#中的.GetWeekOfYear（）？

Question

我想从datetime得到python的yearWeek。我使用了IsoCalender（）[1]，但它返回的星期与我使用的不同日期时间格式info.InvariantInfo.Calendar.GetWeekOfYear（日期，CalendarWeekRule.FirstDay=第一天, 星期一，星期一). 你知道吗

I have tried:

1) IsoCalender()[1].

2) d = datetime.datetime.strptime('2017-09-22 00:00:00.00','%Y-%m-%d %H:%M:%S.%f')
print(datetime.datetime.strftime(d,'%W'))

So For '2017-09-22 00:00:00.00' In C# I get 39 but I get 38 in python using above mentioned techniques.

任何帮助都将受到高度赞扬。你知道吗

Answer 1

根据ISO 8601（参见this draft von 2016, section 5.7.7）

A week is defined as a seven-day time interval, starting with a Monday. Week number one of the calendar year is the first week that contains at least four (4) days in that calendar year.

Python的date.isocalendar文档同样说明：

[…] week starts on a Monday and ends on a Sunday. The first week of an ISO year is the first (Gregorian) calendar week of a year containing a Thursday.

根据documentation of CalendarWeekRule，这等于CalendarWeekRule.FirstFourDayWeek：

Indicates that the first week of the year is the first week with four or more days before the designated first day of the week.

而CalendarWeekRule.FirstDay是指：

Indicates that the first week of the year starts on the first day of the year and ends before the following designated first day of the week.

总之，正确的方法是：

DateTimeFormatInfo.InvariantInfo.Calendar.GetWeekOfYear(new DateTime(2017, 9, 22), CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday)

正确的结果是38。你知道吗