python 计算一年内的所有周的具体日期详解编程语言

#!/usr/bin/env python 
# -*- coding:utf-8 -*- 
import datetime 
import collections 
def date_list_fun(starttime,endtime): 
    '''计算输入的起始日期和结束日期之间的所有日期''' 
    _u=datetime.timedelta(days=1) 
    startdate=datetime.datetime.strptime(starttime,'%Y%m%d') 
    enddate=datetime.datetime.strptime(endtime,'%Y%m%d') 
    n=0 
    date_list=[] 
    if  startdate<=enddate: 
        # print startdate,enddate 
        while 1: 
            _time=startdate+n*_u 
            date_list.append(_time.strftime('%Y%m%d')) 
            n=n+1 
            if _time==enddate: 
                break 
    return date_list 
def allweeks(year): 
    '''计算一年内所有周的具体日期,从1月1号开始，12.31号结束 
    输出如{1: ['20190101','20190106'],...} 只有六天 
    ''' 
    start_date=datetime.datetime.strptime(str(year)+'0101','%Y%m%d') 
    end_date=datetime.datetime.strptime(str(year)+'1231','%Y%m%d') 
    _u=datetime.timedelta(days=1) 
    n=0 
    week_date={} 
    while 1: 
        _time=start_date+n*_u 
        w=str(int(_time.strftime('%W'))+1) 
        week_date.setdefault(w,[]).append(_time.strftime('%Y%m%d')) 
        n=n+1 
        if _time==end_date: 
            break 
    week_date_start_end={} 
    for i in week_date: 
       week_date_start_end[i]=[week_date[i][0],week_date[i][-1]] 
    print   week_date 
    print week_date_start_end 
    return week_date 
  
def all_weeks(year): 
    '''计算一年内所有周的具体日期,每周都是7天，可能最后一周到 下年 
     week_date 输出如{1: ['20181231', '20190101', '20190102', '20190103', '20190104', '20190105', '20190106'],...} 
     计算一年内所有周的起始日期 
     week_date_start_end {1: ['20181231','20190106'],...} 
     ''' 
  
    start_date=datetime.datetime.strptime(str(int(year)-1)+'1224','%Y%m%d') 
    end_date=datetime.datetime.strptime(str(int(year)+1)+'0107','%Y%m%d') 
    _u=datetime.timedelta(days=1) 
    n=0 
    week_date={} 
    while 1: 
        _time=start_date+n*_u 
        y,w=_time.isocalendar()[:2] 
        if y==year : 
            week_date.setdefault(w,[]).append(_time.strftime('%Y%m%d')) 
        n=n+1 
        if _time==end_date: 
            break 
    week_date_start_end={} 
    for i in week_date: 
       week_date_start_end[i]=[week_date[i][0],week_date[i][-1]] 
    print   week_date 
    # print week_date_start_end 
    return week_date,week_date_start_end