为什么这个 class 程序没有 return 余额？

Question

问题：开发一个支持这些方法的classBankAccount： __init__()：将银行账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()：取一个参数作为输入，从余额中取出

deposit()：取一个金额作为输入，添加到余额中

balance():Returns账户余额

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

访问类实例变量，而不是函数参数。无需将 amount 传递给函数只是为了 return it

Answer 2

余额定义应该是这样的：

def balance(self):
    return self.balance

您可能还想考虑将变量名称从 balance 更改为 accountBalance，这样它就不会影响同名的定义。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 class 程序没有 return 余额？

Why does this class program not return the balance?

python

account

class