NameError：名称“”未定义[关闭]

Question

我下面的代码应该将客户对象的 describe 方法的返回值打印到终端……但事实并非如此。问题似乎是 NameError: name 'price' is not defined。

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())

谁能告诉我我错过了什么？

Answer 1

你没有打电话给calculate_ticket_price。

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

注意calculate_ticket_price 可以或者接受age 参数，在这种情况下它不需要假设self.age 存在：

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

或者您可以做出这样的假设并完全摆脱 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

那么describe 的主体将简单地省略任何显式参数：

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

---

在前者中，请注意您在定义中根本不使用self ；这表明它应该是一个静态方法，或者只是一个可以被Customer 使用的常规函数​​，而不需要任何混合类。

Answer 2

切普纳是正确的。您必须在 init 函数中调用 calculate_ticket_price。正确的语法是使用 super 关键字。

例子：

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}"

您可以点击here了解更多关于超级关键字的信息。