35、计算日期数据周同比

题目：

  计算日期数据周同比？

2022-04-16 62
2022-04-17 82
2022-04-18 97
2022-04-19 75
2022-04-20 93
2022-04-21 90
2022-04-22 90
2022-04-23 61
2022-04-24 81
2022-04-25 79
2022-04-26 88
2022-04-27 75
2022-04-28 85
2022-04-29 82
2022-04-30 71
2022-05-01 67
2022-05-02 64
2022-05-03 84
2022-05-04 72

思路：

  1、创建新字典，读取文件内容，将数据遍历添加进字典中。

  2、定义一个格式化初始日期和七天后日期的函数

  3、遍历字典中的日期和值，将值进行处理输出。

结果：

import datetime
date_sale = {}

is_first_line = True
with open("./text") as fin:
    for line in fin:
        line = line[:-1]
        date,sale_number = line.split(" ")
        date_sale[date] = float(sale_number)

def get_diff_days(date,days):
    curr_date = datetime.datetime.strptime(date,"%Y-%m-%d")
    timedelta = datetime.timedelta(days=-days)
    return (curr_date + timedelta).strftime("%Y-%m-%d")

for date,sale_number in date_sale.items():
    date7 = get_diff_days(date,7)
    sale_number7 = date_sale.get(date7,0)
    if sale_number7 == 0:
        print(date,sale_number,0)
    else:
        week_diff = (sale_number - sale_number7) / sale_number7
        print(date,sale_number,date7,sale_number7,week_diff)