输入1 可以持续添加数字，

输入2可以查看所有数字

输入数字0，退出系统

进行需求分析，编写简单的代码实现功能（本练习非常基础，有待完善）

import json
import os.path
import time

menu = """输入1 可以持续添加数字，
输入2可以查看所有数字
输入数字0，退出系统"""

items = []
FILE_PATH = "./items.json"


def save_data():                    #存储
    with open(FILE_PATH, "w") as f:
        json.dump(items, f)


def load_data():
    if os.path.exists(FILE_PATH):   #加载
        with open(FILE_PATH, "r") as f:
            for data in json.load(f):
                items.append(data)


def check_option():
    while True:
        print(menu)
        option = input("请输入选项")
        if option not in ["0", "1", "2"]:#简单判断用户输入
            print(f"输入不合法！重新输入")
        return option


def add_num():
    while True:
        value = int(input("添加数字："))
        items.append(value)
        print(f"添加成功！")
        save_data()
        while True:
            select_yn = input("继续添加（y）,退至菜单（n）")#判断用户是否继续输入
            if select_yn not in ["y", "Y", "n", "N"]:
                print(f"输入不合法！")
            elif select_yn == "y" or select_yn == "Y":
                break
            elif select_yn == "n" or select_yn == "N":
                break
        if select_yn == "n" or select_yn == "N":
            break




def look_all_num():
    if items:     #进行简单的判断items是否为空
        for item in items:
            print(item)
    else:
        print(f"还没有添加数字")


def quit_system():
    print(f"退出系统中。。。")
    time.sleep(2)   #简单的系统休眠时间
    print(f"退出成功！")


load_data()


def main():
    while True:
        option = check_option()
        if option == "1":
            while True:
                add_num()
        elif option == "2":
            look_all_num()
        elif option == "0":
            quit_system()
            break


main()