'''
设计者：ISDF
版本：v3..0
日期：04/01/2019
'''
'''
设计者：ISDF
版本：v4..0
日期：03/27/2024

'''
import datetime

#闰年判断函数
def ys_leep_year(year):
    ys_leep = False
    if (year % 400 == 0) or ((year % 4 == 0) and (year % 100 != 0)):
        ys_leep = True
    return  ys_leep

def main():
    input_date_string = input("请输入日期(yyyy/mm/dd):")
    date = datetime.datetime.strptime(input_date_string,"%Y/%m/%d")
    # input(date)
    year = date.year
    month = date.month
    day = date.day
    days=0
    days += day

    #计算之前当前月份的天数总和
    days_in_month_dict= {1:31,2:28,3:31,4:30,5:31,6:30,
                        7:31,8:31,9:30,10:31,11:30,12:31}
 
    if ys_leep_year(year):
        days_in_month_dict[2] = 29
    i = 1
    for i in range(1,month):
        days += days_in_month_dict[i]
    # days = sum(days_in_month)[:month - 1]) + day
    print("这是第{}天".format(days))

if __name__ == '__main__':
    main()

运行结果：