Python面向對象的固定帳戶

Question

我需要儲蓄帳戶不能更改爲小於500的值。構造器餘額不應接受任何低於500的值。代碼運行良好且沒問題。存款和取款方法正常工作，但我不知道如何防止其餘額低於500的變量訪問儲蓄賬戶。

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 

你也可以自定義一個例外：

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