python - 一年中的日历周数？

Question

在 Python 中，我们如何找出一年中的日历周数？

我没有在标准库中找到函数。

然后我想到了 date(year, 12, 31).isocalendar()[1]，但是

For example, 2004 begins on a Thursday, so the first week of ISO year 2004 begins on Monday, 29 Dec 2003 and ends on Sunday, 4 Jan 2004, so that date(2003, 12, 29).isocalendar() == (2004, 1, 1) and date(2004, 1, 4).isocalendar() == (2004, 1, 7).

Answer 1

根据相同的 ISO 规范，1 月 4 日总是将成为给定年份的第 1 周。通过同样的计算，12 月 28 日总是在一年的最后一周。您可以使用它来查找给定年份的最后一周数:

from datetime import date, timedelta

def weeks_for_year(year):
    last_week = date(year, 12, 28)
    return last_week.isocalendar()[1]

另请参阅维基百科、ISO 周文章 lists all properties of the last week :

• It has the year's last Thursday in it.
• It is the last week with a majority (4 or more) of its days in December.
• Its middle day, Thursday, falls in the ending year.
• Its last day is the Sunday nearest to 31 December.
• It has 28 December in it. Hence the latest possible dates are 28 December through 3 January, the earliest 21 through 28 December.

要进行更全面的周计算，您可以使用 isoweek module ;它有一个 Week.last_week_of_year() 类方法:

>>> import isoweek
>>> isoweek.Week.last_week_of_year(2014)
isoweek.Week(2014, 52)
>>> isoweek.Week.last_week_of_year(2014).week
52