如何使用 Python 确定从星期日开始的一年中的第几周？

Question

我需要从星期日开始计算一年中的第几周。默认的 ISO 周从星期一开始，但我的要求是星期日作为一周的开始。

例如 2019-01-06 是 星期日，应该是第 2 周。

我试过了

t1.strftime("%U")

但问题是它在第一个星期日之前的新年中的所有日子都返回 0，并从一年中的第一个星期日开始计算周数。

提前感谢您的帮助。

Answer 1

有点hacky，但这样就可以了：

import datetime


def week(t):
    if datetime.datetime(t.year, 1, 1).weekday() == 6:
        # The year started with a Sunday.
        incr = 0
    else:
        incr = 1
    return int(t.strftime("%U")) + incr


ls = [datetime.datetime(2019, 1, 5), datetime.datetime(2019, 1, 6),
      datetime.datetime(2019, 8, 3), datetime.datetime(2019, 8, 4),
      datetime.datetime(2017, 1, 1)]

for t in ls:
    print("day:", t.strftime("%Y-%m-%d %a,"), "week:", week(t))

Output:

day: 2019-01-05 Sat, week: 1
day: 2019-01-06 Sun, week: 2
day: 2019-08-03 Sat, week: 31
day: 2019-08-04 Sun, week: 32
day: 2017-01-01 Sun, week: 1

Answer 2

共享我的代码，实现方式与您的稍有不同。 我考虑到一年的第一天可能属于去年的一周。不过，您可以根据自己的需要调整此代码。

下面给出的代码片段 returns year_wk 对于任何 'given_date' 和
一周从任何 day_no 开始（它是 4，即下面代码中的星期五）

import math as mt
import datetime as dt    

def get_first_date_year(year, day_no):
    d1 = dt.date(year, 1, 1)
    return d1 + dt.timedelta((day_no - d1.weekday())%7)

def get_yearwk_from_date(given_date, day_no):
    first_date = get_first_date_year(given_date.year, day_no)
    if (given_date < first_date):
        first_date = get_first_date_year(given_date.year-1, day_no)
    return first_date.year*100 + mt.ceil(((given_date - first_date).days+1)/7)

FRIDAY = 4
for i in range(20):
    given_date = dt.date(2018, 12, 23) + dt.timedelta(days=i)
    year_wk = get_yearwk_from_date(given_date, FRIDAY)
    print("Date: "+str(given_date)+", YearWeek: "+str(year_wk))

输出：

Date: 2018-12-23, YearWeek: 201851
Date: 2018-12-24, YearWeek: 201851
Date: 2018-12-25, YearWeek: 201851
Date: 2018-12-26, YearWeek: 201851
Date: 2018-12-27, YearWeek: 201851
Date: 2018-12-28, YearWeek: 201852
Date: 2018-12-29, YearWeek: 201852
Date: 2018-12-30, YearWeek: 201852
Date: 2018-12-31, YearWeek: 201852
Date: 2019-01-01, YearWeek: 201852
Date: 2019-01-02, YearWeek: 201852
Date: 2019-01-03, YearWeek: 201852
Date: 2019-01-04, YearWeek: 201901
Date: 2019-01-05, YearWeek: 201901
Date: 2019-01-06, YearWeek: 201901
Date: 2019-01-07, YearWeek: 201901
Date: 2019-01-08, YearWeek: 201901
Date: 2019-01-09, YearWeek: 201901
Date: 2019-01-10, YearWeek: 201901
Date: 2019-01-11, YearWeek: 201902

如何使用 Python 确定从星期日开始的一年中的第几周？

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