python - 为什么覆盖我的方法会导致我的属性停止正常工作？

Question

我们在计算机科学类(class)中一直在学习面向对象编程，但作为示例提供的代码似乎无法正常工作。

class bankAccount(): 

    '''This is a bank account class'''

    def __init__(self, account_name = "Bank Account", balance = 1500):
        self.__account_name = account_name 
        self.__balance = balance 

    def deposit(self, value): 
        self.__balance = self.__balance + value 
        print("You now have: ", self.__balance) 

    def withdraw(self, value): 
        self.__balance = self.__balance - value 
        print("You now have: ", self.__balance) 

class currentAccount(bankAccount): 

    '''This is a current account class''' 

    def __init__(self, account_name = "Current Account", balance = 1500): 
        self.__account_name = account_name 
        self.__balance = balance

        super().__init__() 

    def withdraw(self, value): 

        if value > 1000: 
            print("You will have to phone the bank manager") 

        else: 
            self.__balance = self.__balance - value 
            print("You now have: ", self.__balance) 

class savingsAccount(bankAccount): 

    '''This is a current account class''' 

    def __init__(self, account_name = "Savings Account", balance = 1500): 
        self.__account_name = account_name 
        self.__balance = balance 

        super().__init__() 

    def deposit(self, value): 
        self.__balance = self.__balance + (value *1.03) 
        print("You now have: ", self.__balance) 

currentObject = currentAccount() 

savingsObject = savingsAccount() 

while True: 
    print("1. Current Account") 
    print("2. Savings Account")

    menu_option = int(input()) 

    if menu_option == 1: 
        print("1. Deposit funds") 
        print("2. Withdraw funds") 

        submenu_option = int(input()) 

        if submenu_option == 1: 
            value = int(input("How much would you like to deposit? ")) 
            currentObject.deposit(value) 

        elif submenu_option == 2: 
            value = int(input("How much would you like to withdraw? ")) 
            currentObject.withdraw(value) 
        else: 
            print("Wrong menu choice!") 

    elif menu_option == 2: 
        print("1. Deposit funds") 
        print("2. Withdraw funds")

        submenu_option = int(input()) 

        if submenu_option == 1: 
            value = int(input("How much would you like to deposit? ")) 
            savingsObject.deposit(value) 

        elif submenu_option == 2: 
            value = int(input("How much would you like to withdraw? ")) 
            savingsObject.withdraw(value) 

        else: 
            print("Wrong menu choice!") 

    else: 
        print("Wrong menu choice!") 

input() 

似乎每次取款和存款都会存储单独的数据。例如，如果您从储蓄账户存入 100 美元，然后提取 100 美元，则程序似乎会默认使用 1500 作为初始余额，而不是从 (1500 + 100) = 1600 然后执行 (1600 - 100)您存款和取款时的余额。

任何帮助将不胜感激，因为 OOP 对我来说是新的，我不明白为什么会发生这种情况。

Answer 1

造成困惑的原因是您使用了self.__balance。属性名称中的双下划线是激活名称修改的特殊情况: What is the meaning of a single and a double underscore before an object name?

要解决您的问题，只需将所有类属性名称切换为单个下划线前缀:

class bankAccount(): 

    '''This is a bank account class'''

    def __init__(self, account_name = "Bank Account", balance = 1500):
        self._account_name = account_name 
        self._balance = balance 

    def deposit(self, value): 
        self._balance = self._balance + value 
        print("You now have: ", self._balance) 

    def withdraw(self, value): 
        self._balance = self._balance - value 
        print("You now have: ", self._balance) 

class currentAccount(bankAccount): 

    '''This is a current account class''' 

    def __init__(self, account_name = "Current Account", balance = 1500): 
        self._account_name = account_name 
        self._balance = balance

        super().__init__() 

    def withdraw(self, value): 

        if value > 1000: 
            print("You will have to phone the bank manager") 

        else: 
            self._balance = self._balance - value 
            print("You now have: ", self._balance) 

class savingsAccount(bankAccount): 

    '''This is a current account class''' 

    def __init__(self, account_name = "Savings Account", balance = 1500): 
        self._account_name = account_name 
        self._balance = balance 

        super().__init__() 

    def deposit(self, value): 
        self._balance = self._balance + (value *1.03) 
        print("You now have: ", self._balance) 

currentObject = currentAccount() 

savingsObject = savingsAccount() 

while True: 
    print("1. Current Account") 
    print("2. Savings Account")

    menu_option = int(input()) 

    if menu_option == 1: 
        print("1. Deposit funds") 
        print("2. Withdraw funds") 

        submenu_option = int(input()) 

        if submenu_option == 1: 
            value = int(input("How much would you like to deposit? ")) 
            currentObject.deposit(value) 

        elif submenu_option == 2: 
            value = int(input("How much would you like to withdraw? ")) 
            currentObject.withdraw(value) 
        else: 
            print("Wrong menu choice!") 

    elif menu_option == 2: 
        print("1. Deposit funds") 
        print("2. Withdraw funds")

        submenu_option = int(input()) 

        if submenu_option == 1: 
            value = int(input("How much would you like to deposit? ")) 
            savingsObject.deposit(value) 

        elif submenu_option == 2: 
            value = int(input("How much would you like to withdraw? ")) 
            savingsObject.withdraw(value) 

        else: 
            print("Wrong menu choice!") 

    else: 
        print("Wrong menu choice!") 

input()