今日または指定された日を起点とした次のプレミアムフライデーの日付を取得する

next_premium_friday.py

from datetime import date, timedelta


def next_premium_friday(offset=None):
    if offset is None:
        offset = date.today()

    if offset.month == 12:
        end_of_month = date(offset.year + 1, 1, 1) - date.resolution
    else:
        end_of_month = date(offset.year, offset.month + 1, 1) - date.resolution

    end_of_month_weekday = end_of_month.weekday()

    premium_friday = end_of_month - timedelta(days=(3 + end_of_month_weekday) % 7)

    if offset > premium_friday:
        if offset.month == 12:
            next_month = date(offset.year + 1, 1, 1)
        else:
            next_month = date(offset.year, offset.month + 1, 1)
        return next_premium_friday(next_month)
    else:
        return premium_friday

if __name__ == '__main__':
    print(next_premium_friday(date(2017, 2, 24)))
    print(next_premium_friday(date(2017, 2, 25)))