python使用文件处理加函数的方式写ATM简易操作

# import os
# 这里的os模块没有调用，如果是数据量大的话，则需要这个模块
'''
简易版的ATM功能，实现用户充值，转账等功能
文件读取和存取方式采用的是读写同一个文件
优点：占用磁盘空间少
缺点：占用内存空间
ps：也可以采用os模块对文件操作
优点：占用内存空间少
缺点：占用磁盘空间多
两种方式根据自己需求选用！
'''

# 充值功能
def pay_money():
    name_inp = input("请输入要充值的账号：").strip()
    # 调用查询功能查询输入的用户是否存在，若存在将返回账户的余额
    res = pay_check(name_inp)
    res1 = int(res)
    # print(res)
    while 1:
        money_inp = input("请输入充值金额：").strip()
        # 判断输入的金额是否是数字，不是则重新输入
        if not money_inp.isdigit():
            print("请输入的必须是数字".center(50, "*"))
            continue
        money_inp = int(money_inp)

        res1 += money_inp
        # dic[name_inp] += money_inp
        print("充值成功".center(50, "*"))
        # 打开文件，将文件内容读取到内存中。若数据大，则推荐使用os模块
        # 将新的数据写入copy文件然后重命名
        with open("db.txt", "r", encoding="utf8") as f:
            dic = {}
            for line in f:
                user, money = line.strip().split(":")
                dic[user] = int(money)
            if name_inp in dic:
                dic[name_inp] = res1
            else:
                return
        with open("db.txt", "w", encoding="utf8") as w:
            for user, money in dic.items():
                w.write("%s:%s\n" % (user, money))
        break


# 转账功能
def transfer():
    A_name = input("请输入要转账的账户：").strip()
    res_A = pay_check(A_name)
    if res_A < 0:
        return
    B_name = input("请输入要接收的账户：").strip()
    res_B = pay_check(B_name)
    if res_B < 0:
        return

    money = int(input("请输入要转账的金额：").strip())
    res_A1 = int(res_A)
    res_B1 = int(res_B)

    if res_A1 > money:
        res_B1 += money
        res_A1 -= money
        print(res_A1, res_B1)
        print("转账成功".center(50, "*"))

    with open("db.txt", "r", encoding="utf8") as f:
        dic = {}
        for line in f:
            user, money = line.strip().split(":")
            dic[user] = int(money)
        dic[A_name] = res_A1
        dic[B_name] = res_B1
    with open("db.txt", "w", encoding="utf8") as w:
        for user, money in dic.items():
            w.write("%s:%s\n" % (user, money))


# 取现功能
def pay_cash():
    A_name = input("请输入要提现的账户：").strip()
    res_A = pay_check(A_name)
    if res_A < 0:
        return

    while 1:
        money = input("请输入要提现的金额：").strip()
        if not money.isdigit():
            print("输入的金额必须是数字".center(50, "*"))
        money = int(money)

        if money > res_A:
            print("提现金额不足...".center(50, "*"))
        else:
            res_A -= money
            print("取现成功".center(50, "*"))

        with open("db.txt", "r", encoding="utf8") as f:
            dic = {}
            for line in f:
                user, money = line.strip().split(":")
                dic[user] = int(money)
            # if A_name in dic:
            dic[A_name] = res_A
        with open("db.txt", "w", encoding="utf8") as w:
            for user, money in dic.items():
                w.write("%s:%s\n" % (user, money))
        break


# 查询功能
def pay_check(name):
    dic = {}
    with open("db.txt", "r", encoding="utf8") as f:
        for line in f:
            user, money = line.strip().split(":")
            dic[user] = int(money)

    if name not in dic:
        print("用户不存在")
        choice = input("是否需要注册账户（Y/N）：").strip()
        if choice.upper() == "Y":
            pay_register()
        else:
            print("结束本次操作".center(50, "*"))
            return -1
    else:
        print("账户【%s】的余额【%s】" % (name, dic[name]))
        return dic[name]


# 注册功能
def pay_register():
    username = input("请输入你要注册的账户：").strip()
    while 1:
        money_inp = input("请输入你要充值的金额：").strip()
        if not money_inp.isdigit():
            print("请输入数字！".center(50, "*"))
            continue
        else:
            print("充值成功！".center(50, "*"))
            money_inp = int(money_inp)

        with open("db.txt", "a", encoding="utf8") as f:
            f.write("%s:%s\n" % (username, money_inp))
        return


# 执行代码
def my_choice():
    msg = """
        "1": "充值",
        "2": "转账",
        "3": "取现",
        "4": "查询",
        "5": "注册",
        "6": "退出"
    """
    msg_dic = {
        "1": pay_money,
        "2": transfer,
        "3": pay_cash,
        "4": pay_check,
        "5": pay_register,
    }
    while 1:
        print(msg)
        choice = input("请输入你要做的操作：").strip()
        if choice == "6": break
        if choice not in msg_dic:
            print("输入有误，重新输入！".center(50, "*"))
            continue
        if choice == '4':  #
            data = input(">>>>输入账户：").strip()
            msg_dic[choice](data)
            continue
        msg_dic[choice]()


if __name__ == "__main__":
    my_choice()