Question

问题：开发支持这些方法的类BankAccount： __init__()：将银行帐户余额初始化为输入参数的值，如果没有给出输入参数，则初始化为0

withdraw()：将参数作为输入并从余额中提取

deposit()：将金额作为输入并将其添加到余额

balance()：返回帐户中的余额

class ValueErrorException (Exception):
    pass

class BankAccount:

    accounts = 0

    def __init__ (self, bal = 0.0):
        BankAccount.accounts += 1
        self.accountNumber = str(BankAccount.accounts)
        self.balance = bal


    def withdraw(self, amount):
        if self.balance - amount < 0:
            raise ValueErrorException("Illegal balance")
        else:
            self.balance -= amount


    def deposit (self, amount):
        self.balance += amount


    def balance(self, amount):
        return amount

Answer 1

return self.balance

访问classes实例变量，而不是函数参数。无需将金额传递给函数只是为了返回它

Answer 2

余额定义应如下：

def balance(self):
    return self.balance

您可能还需要考虑将变量名称从balance更改为accountBalance，这样它就不会影响名称相同的定义。您的新代码现在是：

class ValueErrorException (Exception):

    pass

class BankAccount:

    accounts = 0

    def __init__ (self, bal = 0.0):
        BankAccount.accounts += 1
        self.accountNumber = str(BankAccount.accounts)
        self.accountBalance = bal


    def withdraw(self, amount):
        if self.accountBalance - amount < 0:
            raise ValueErrorException("Illegal balance")
        else:
            self.accountBalance -= amount


    def deposit (self, amount):
        self.accountBalance += amount


    def balance(self):
        return self.accountBalance

为什么这个班级课程没有返回余额？

2 个答案: