基于起始日期不同的日期创建年周

from datetime import datetime, timedelta

def get_week_number(date_str, start_day='Monday'):
    """
    根据给定的日期字符串和起始日计算年周数
    :param date_str: 日期字符串，格式为 'YYYY-MM-DD'
    :param start_day: 一周的起始日，默认为 'Monday'
    :return: 年周数 (YYYYWW)
    """
    date = datetime.strptime(date_str, '%Y-%m-%d')
    days_of_week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']
    start_day_index = days_of_week.index(start_day)
    
    # 计算给定日期是星期几
    date_day_index = date.weekday()
    
    # 计算距离起始日的天数差
    days_diff = (date_day_index - start_day_index) % 7
    
    # 计算年周的开始日期
    week_start_date = date - timedelta(days=days_diff)
    
    # 计算年周数
    year = week_start_date.year
    week_number = week_start_date.isocalendar()[1]
    
    return f"{year}{week_number:02d}"

# 示例使用
date_str = '2023-10-05'
start_day = 'Monday'
week_number = get_week_number(date_str, start_day)
print(f"The week number for {date_str} starting on {start_day} is {week_number}")