重写OOP类方法致银行账户属性异常，求助问题排查

Let's break down why your balance isn't updating correctly between deposits and withdrawals, and fix the code step by step:

The Root Problem #

Your child classes (currentAccount and savingsAccount) are making two critical mistakes in their __init__ methods:

1. They define their own private __account_name and __balance attributes before calling super().__init__(). In Python, double-underscore ("private") attributes are name-mangled—meaning __balance in currentAccount becomes _currentAccount__balance, while the parent bankAccount's __balance is _bankAccount__balance. These are two completely separate variables.
2. When you call super().__init__() without passing arguments, it initializes the parent's attributes to default values (account_name="Bank Account", balance=1500)—creating conflicting, unlinked state between parent and child.

So when you run savingsObject.deposit(value), you're modifying _savingsAccount__balance, but savingsObject.withdraw(value) uses the parent's method which edits _bankAccount__balance. That's why your balance seems to reset—you're working with two separate balances!

The Fixed Code #

Here's the adjusted code with consistent balance tracking:

class bankAccount():
    '''This is a bank account class'''
    def __init__(self, account_name = "Bank Account", balance = 1500):
        # Use single underscore for protected attributes (accessible to child classes)
        self._account_name = account_name
        self._balance = balance

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

    def withdraw(self, value):
        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):
        # Pass custom values to parent constructor instead of redefining attributes
        super().__init__(account_name, balance)

    def withdraw(self, value):
        if value > 1000:
            print("You will have to phone the bank manager")
        else:
            self._balance -= value
            print("You now have: ", self._balance)

class savingsAccount(bankAccount):
    '''This is a savings account class'''  # Fixed docstring typo
    def __init__(self, account_name = "Savings Account", balance = 1500):
        # Pass custom values to parent constructor
        super().__init__(account_name, balance)

    def deposit(self, value):
        # Use the shared _balance attribute
        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")
    try:
        menu_option = int(input())
    except ValueError:
        print("Please enter a valid number!")
        continue
        
    if menu_option == 1:
        print("1. Deposit funds")
        print("2. Withdraw funds")
        try:
            submenu_option = int(input())
        except ValueError:
            print("Please enter a valid number!")
            continue
            
        if submenu_option == 1:
            try:
                value = int(input("How much would you like to deposit? "))
                currentObject.deposit(value)
            except ValueError:
                print("Please enter a valid amount!")
        elif submenu_option == 2:
            try:
                value = int(input("How much would you like to withdraw? "))
                currentObject.withdraw(value)
            except ValueError:
                print("Please enter a valid amount!")
        else:
            print("Wrong menu choice!")
    elif menu_option == 2:
        print("1. Deposit funds")
        print("2. Withdraw funds")
        try:
            submenu_option = int(input())
        except ValueError:
            print("Please enter a valid number!")
            continue
            
        if submenu_option == 1:
            try:
                value = int(input("How much would you like to deposit? "))
                savingsObject.deposit(value)
            except ValueError:
                print("Please enter a valid amount!")
        elif submenu_option == 2:
            try:
                value = int(input("How much would you like to withdraw? "))
                savingsObject.withdraw(value)
            except ValueError:
                print("Please enter a valid amount!")
        else:
            print("Wrong menu choice!")
    else:
        print("Wrong menu choice!")
input()

Key Changes Explained #

1. Switched to protected attributes: Changed __account_name/__balance to _account_name/_balance. Single underscores signal "protected"—child classes can safely access these attributes while still discouraging direct modification outside the class hierarchy.
2. Removed redundant child class initialization: Instead of redefining attributes in child __init__, we pass custom defaults directly to super().__init__(), ensuring only one set of attributes exists per account instance.
3. Added input validation: Wrapped input conversions in try/except blocks to handle non-numeric inputs gracefully (a robustness upgrade).
4. Fixed docstring typo: Corrected the savingsAccount docstring to match its purpose.

Now deposits and withdrawals will modify the same balance, so your account state stays consistent across operations.

内容的提问来源于stack exchange，提问作者T Burnard