在基于 "ATM" 的程序中使用什么方法

Question

我已经开始分配 ATM 代码，我应该以某种方式使用文本文件。到目前为止我得到了这个：

print("Hello, and welcome to the ATM machine!\n")

a_pin = {1111, 2222, 3333, 4444}

def process():
    pin = int(input("\nplease enter below your 4-digit pin number: "))
    if pin in a_pin:
        if pin == (1111):
            f = open("a.txt", "r")
        elif pin == (2222):
            f = open("b.txt", "r")
        elif pin == (3333):
            f = open("c.txt", "r")
        elif pin == (4444):
            f = open("d.txt", "r")
        print(
    """
        MENU:
        1: view your current balance
        2: make a withdraw
        3: make a deposit
        4: exit

     """)

        option = input("\nwhat would you like to do? ")

        if option == "1":
            print(f.read())
        elif option == "2":
            y = str(input("\nHow much would you like you like to withdraw? "))
            f.write(y)
            print("Excellent, your transaction is complete!")
        elif option == "3":
            z = str(input("\nHow much would you like to deposit? "))
            f.write(z)
            print("Excellent, your transaction is complete!")
        elif option == "4":
            input("Please press the enter key to exit.")



    else:
        print("\nthat was a wrong pin number!")
        x = input("\nwould you like to try again? '(y/n)' ")
        if x == "y":
            process()
        else:
            input("\npress the enter key to exit.")

process()

代码目前有效，但我想通过询问 withdrawing/depositing 时如何最有效地覆盖文本文件上的内容来节省一些时间。我在考虑 pickled 文件……但是我会很高兴收到任何建议，因为如果我想在 withdraw/deposit 之后向用户显示新的 ammount，那么像 write 这样的普通命令对这个任务真的不起作用。非常感谢！

Answer 1

重点是考虑必要的"mode"打开文件，这样既可以读取(r)又可以修改(r+):

if pin == (1111):
        f = open("a.txt", "r+")
    elif pin == (2222):
        f = open("b.txt", "r+")
    elif pin == (3333):
        f = open("c.txt", "r+")
    elif pin == (4444):
        f = open("d.txt", "r+")

然后将当前余额存入文件，每次交易后更新。

# read current balance from file and save its value
bal = float(f.read().strip('\n'))  # or replace float() with int()

# reset file pointer to beginning of file before updating contents
f.seek(0)

if option == '1':
    print(f.read()) # or simply, print(bal)
elif option == '2':
    y = str(input("\nHow much would you like you like to withdraw? "))
    bal -= int(y)            # calculate new balance
    f.write(str(bal)+'\n')   # write new balance to file as a string
    print("Excellent, your transaction is complete!")
elif option == '3':
    z = str(input("\nHow much would you like to deposit? "))
    bal += int(z)
    f.write(str(bal)+'\n')
    print("Excellent, your transaction is complete!")

Answer 2

如果你只保留最新的余额，尝试以w+模式打开文本文件，读取整行并将值保留在你的程序中，随意修改它最后写入结束值并添加行尾。如果每次运行程序都应该更新该值。

在基于 "ATM" 的程序中使用什么方法

What method to use in "ATM" based program

python

pseudocode