NameError:未定义名称"“

Question

下面的代码应该将customer对象的描述方法返回的值打印到没有的terminal...but。问题似乎是NameError:没有定义名称‘价格’。

class TicketMixin:
    
    """ Mixin to calculate ticket price based on age """
    def calculate_ticket_price(self, age):
        
        ticket_price = 0
        price = ticket_price
        
        if self.age < 12:
            price = ticket_price + 0
        elif self.age < 18:
            price = ticket_price + 15
        elif self.age < 60:
            price = ticket_price + 20
        elif self.age >= 60:
            price = ticket_price + 10
        return price

class Customer(TicketMixin):
    """ Create instance of Customer """
    def __init__(self, name, age,):
        self.name = name
        self.age = age
    
    def describe(self):
        return f"{self.name} age {self.age} ticket price is {price}"
        
customer = Customer("Ryan Phillips", 22)
print(customer.describe())

谁能告诉我错过了什么吗？

Answer 1

你没给calculate_ticket_price打电话。

def describe(self):
    return f"{self.name} age {self.age} ticket price is {self.calculate_ticket_price(self.age)}"

请注意，calculate_ticket_price可以采用age参数，在这种情况下，它不需要假设存在self.age：

class TicketMixin:
    
    """ Mixin to calculate ticket price based on age """
    def calculate_ticket_price(self, age):
        
        ticket_price = 0
        price = ticket_price
        
        if age < 12:
            price = ticket_price + 0
        elif age < 18:
            price = ticket_price + 15
        elif age < 60:
            price = ticket_price + 20
        elif age >= 60:
            price = ticket_price + 10
        return price

或者，您可以做这个假设，完全去掉age参数：

class TicketMixin:
    
    """ Mixin to calculate ticket price based on age """
    def calculate_ticket_price(self):
        
        ticket_price = 0
        price = ticket_price
        
        if self.age < 12:
            price = ticket_price + 0
        elif self.age < 18:
            price = ticket_price + 15
        elif self.age < 60:
            price = ticket_price + 20
        elif self.age >= 60:
            price = ticket_price + 10
        return price

然后，describe的主体将简单地省略任何显式的参数：

def describe(self):
    return f"{self.name} age {self.age} ticket price is {self.calculate_ticket_price()}"

在前者中，请注意定义中根本不使用self；这意味着它应该是一个静态方法，或者仅仅是一个Customer可以使用的常规函数，而不需要任何混合类。

Answer 2

切普纳是对的。您必须在您的calculate_ticket_price init函数中调用。正确的语法是使用Super关键字。

示例：

class Customer(TicketMixin):
    """ Create instance of Customer """
    def __init__(self, name, age,):
        self.name = name
        self.age = age
        self.price = super().calculate_ticket_price(self.age)
    
    def describe(self):
        return f"{self.name} age {self.age} ticket price is {self.price}"

您可以通过单击这里来了解有关超级关键字的更多信息。