AttributeError: 'Customer'对象没有属性'get_mailing_list

Question

你好，我在运行下面的代码时遇到了一个错误：
AttributeError: 'Customer' 对象没有 'get_mailing_list' 这个属性。
我在代码里用了 sys 来调用父类，但不太确定怎么才能调用子类。
我还是个编程新手，所以我知道这可能是个“简单”的问题，但我就是想不明白。
提前谢谢你们的帮助。

# This Person class holds general data about people and will
# end up as the superclass for this example.
class Person:
    #__init__ method initialzes the attributes.
    def __init__(self, name, address, phone):
        self.__name = name
        self.__address = address
        self.__phone = phone

    # The set_name method gets the persons name.
    def set_name(self, address):
        self.__name = name

    # The set_address method gets the persons address.
    def set_address(self, address):
        self.__address = address

    # The set_phone method gets the persons phone number.
    def set_phone(self, phone):
        self.__phone = phone

    # The get_name method returns the name.
    def get_name(self):
        return self.__name

    # The get_address method returns the address.
    def get_address(self):
        return self.__address

    # The get_phone method returns the phone number.
    def get_phone(self):
        return self.__phone

# The Customer class holds the general data from superclass Person
# as well as customer number and mailing list info making it a subclass
# of Person.
class Customer(Person):
    # __init__ method initializes the attributes.
    def __init__(self, name, address, phone, customer_number, mailing_list):
        # Call the superclass
        Person.__init__(self, name, address, phone)
        self.__customer_number = customer_number
        self.__mailing_list = mailing_list

        # The set_customer_number method get customer number.
        def set_customer_number(self, customer_number):
            self.__customer_number = customer_number

        # The set_mailing_list method gets yes or no to mailing list.
        def set_mailing_list(self, mailing_list):
            self.__mailing_list = mailing_list

        # The get_customer_number method returns the customer number.
        #def get_customer_number(self):
           # return self.__customer_number

        # The get_mailing_list method returns the yes or no response.
        def get_mailing_list(self):
            return self.__mailing_list

# This program will test the Person superclass and Customer subclass while
# by returning and displaying the gathered information.

import sys

# Get the cutomer info.
name = input('Name: ')
address = input('Address: ')
phone = input('Phone: ')
customer_number = input('Customer number: ')
mail = input('Include in mailing list? (y/n): ')

# Determine True or False for mailing list.
if mail.lower() == 'y':
    mailing_list = True
else:
    mailing_list - False

# Create an instance of the Customer class.
my_customer = Customer(name, address, phone, customer_number, mailing_list)

# Display the object's data.
print('Customer Information')
print('---------------------')
print('Name:', my_customer.get_name())
print('Address:', my_customer.get_address())
print('Phone:', my_customer.get_phone())
#print('Customer number:', my_customer.get_customer_number())
print('Mailing list:', my_customer.get_mailing_list())

Answer 1

你把所有的方法都放在了 Customer 类的 __init__ 里面，而不是直接放在这个类里。

 class Customer(Person):
     def __init__(self, ...):
         ...

     def get_mailing_list(self):  # <-- Notice the indentation level
         return ...