如何从 Python 列表中的项目访问外部 object 属性？

Question

I have a City object that has some attributes, including a list of houses:

city1 = {
    'name': "Tokio",
    'houses': [
        {
            'code': 1,
            'residents': 4
        },
        {
            'code': 2,
            'residents': 2
        }
    ]
}

My problem is that, within each object in the list of houses I need to have a method mount_description(self) that needs to access the name attribute of the external object City where this list of houses is inside:

class House():
    code = None
    residents = 0

    def mount_description(self):
        # get 'name' attribute of the external object

class City():
    name = None
    houses = list()

I know the correct thing would be for the City object to send the name to the items in the list of houses, but unfortunately due to many details I cannot do this. I really need each Home object to be able to access the external object where it is located.

Does anyone know how to do this? Or if this is possible?

Answer 1

Give to the house a reference to its host city

    class House():
        code = None
        residents = 0
        city = None

        def __init__(self, city, code, residents):
            self.city = city
            self.code = code
            self.residents = residents
            #Do what you want here

        def mount_description(self):
            print(self.city.name)

    class City():
        name = None
        houses = list()

        def __init__(self, json):
            for house in json['houses']:
                self.houses.append(House(self, house['code'], house['residents']))
            self.name = json['name']

        def set_name(self, newname):
            self.name = newname

        def print_name(self):
            print(self.name)

Then you can do

city1_json = {
    'name': "Tokio",
    'houses': [
        {
            'code': 1,
            'residents': 4
        },
        {
            'code': 2,
            'residents': 2
        }
    ]
}

city = City(city1_json)


city.print_name()
house1 = city.houses[0]
house1.mount_description()
>>> Tokio
>>> Tokio

city.set_name("Paris")
city.print_name()
house1.mount_description()
>>> Paris
>>> Paris

Answer 2

I think you should need to build something like a most simple tree. For City, you have a list for houses, or children. Each house doesn't know where is located, so need a parent for the house, or city.

class House():

    def __init__(self, code=None, residents=0):
        self.code = code
        self.residents = residents
        self.parent = None

    @property
    def city(self):
        # get 'name' attribute of the external object
        if self.parent:
            return self.parent.name
        else:
            return None

class City():

    def __init__(self, name):
        self.name = name
        self.houses = list()

    def add_house(self, house):
        self.houses.append(house)
        house.parent = self

    def add_houses(self, houses):
        self.houses += houses
        for house in houses:
            house.parent = self

city_1 = City('Tokyo')
house_1 = House(code=1, residents=4)
house_2 = House(code=2, residents=2)
city_1.add_house(house_1)
city_1.add_house(house_2)

city_2 = City('Chicago')
house_3 = House(code=1, residents=3)
house_4 = House(code=2, residents=5)
city_2.add_houses([house_3, house_4])

>>> house_1.city, house_3.city
('Tokyo', 'Chicago')