Python面向对象的固定账户

Question

我需要储蓄帐户不被更改为小于500的值。构造函数balance不应接受任何低于500的值。代码运行良好，一切正常。存取款方法可以正常工作，但我不知道如何防止余额小于500的变量访问储蓄帐户。

class BankAccount(object):
    def __init__(self):
        pass

    def withdraw(self):
        pass

    def deposit(self):
        pass


class SavingsAccount(BankAccount):
    def __init__(self, balance=500):
        self.balance = balance

    def deposit(self, deposit):
        if self.deposit > 0:
            self.balance += deposit
            return self.balance
        else:
            return "Invalid deposit amount"

    def withdraw(self, withdraw):
        if self.balance < withdraw:
            return "Cannot withdraw beyond the current account balance"
        elif (self.balance - withdraw) < 500:
            return "Cannot withdraw beyond the minimum account balance"
        elif withdraw < 0:
            return "Invalid withdraw amount"
        else:
            self.balance -= withdraw
            return self.balance


class CurrentAccount(BankAccount):
    def __init__(self, balance=0):
        self.balance = balance

    def deposit(self, deposit):
        if self.deposit > 0:
            self.balance += deposit
            return self.balance
        else:
            return "Invalid deposit amount"

    def withdraw(self, withdraw):
        if withdraw < 0:
            return "Invalid withdraw amount"
        elif self.balance < withdraw:
            return "Cannot withdraw beyond the current account balance"
        else:
            self.balance -= withdraw
            return self.balance

Answer 1

class SavingsAccount(BankAccount):
    def __init__(self, balance=500):
        if balance < 500:
            raise ValueError("SavingsAccount balance must be at least 500")
        self.balance = balance

您还可以定义自定义异常：

class BalanceTooLowError(ValueError):
    """Raise if attempting to set an account balance to a disallowed value"""