案例：快递柜存取验证码管理器

import random

def welcome():
    print("*" * 40)
    print("欢迎您来到快递存储柜：请您选择操作（1，2）")
    print("1. 存快递            2. 取快递")
    print("*" * 40)
    return input("请选择您的操作（1，2）：")

def generate_code():
    seeds = '1234567890'
    random_str = ''

    for _ in range(4):
        random_str += random.choice(seeds)

    return random_str

def store():
    with open('./file.txt', 'a+') as f:
        random_str = generate_code()
        f.write(random_str + ' ')
        print('您的物品已存放，取货码是：' + random_str)

def fetch():
    num = input('请输入您的取货码：')

    with open('./file.txt', 'r+') as f:
        all_nums = f.read()

        if all_nums != '':
            list_nums = all_nums.split(' ')
            if num in list_nums:
                print('物品已出柜，请您拿好')
                list_nums.remove(num)
                all_nums = ' '.join(list_nums)
                f.seek(0)
                f.truncate()
                f.write(all_nums)
            else:
                print('对不起，无此取货码')
        else:
            print('取货码不正确，此柜已无货品')

flag = 'y'
while flag == 'y':
    words = welcome()

    if words == '1':
        store()
    elif words == '2':
        fetch()
    else:
        print('只能输入1或2')
        continue
    
    flag = input('是否继续（y/n）：')