从内部类引用父对象实例

Question

我正在尝试创建一个语法友好的库，它不需要用户不断地传递凭据或键入多余或过多的语句。我的策略是专注于我希望库语法的外观，然后设计库以这种方式运行。我知道我可以实现以下内容：

api = Api(user="admin", pswd="blahblah")

new_order = api.Order()
new_order.status = "pending"
api.create(new_order)
api.order_assign_user(new_order, user)

existing_order = api.get_order(orderId=12345)
existing_order.status = "shipped"
api.update(existing_order)

使用类似下面的东西：

class Api(object):
    def __init__(self, user=None, pswd=None):
        self.user = user
        self.pswd = pswd

    class Order(api):
        def __init__ (self, status=None):
            self.status = status

    def create(self, x):
        auth = Auth(self.user, self.pswd)
        # use authorization credentials to create data remotely
        return x

    def update(self, x):
        auth = Auth(self.user, self.pswd)
        # use authorization credentials to update data from remote
        return x

    def get_order(self, orderId=None):
        auth = Auth(self.user, self.pswd)
        # use authorization credentials to update data from remote
        return order

---

但我希望能够使用以下语句：

new_order.create() # instead of api.create(new_order)

new_order.assign_user(user) # instead of api.order_assign_user(new_order, user)

existing_order = api.Order.get(orderId=12345) # returns retrieved Order Instance

这给我带来了一个问题：

如何让Order() 实例访问创建它的Api() 实例的属性？如果无法访问这些，任何属性（如“user”和“pswd”）都将无法访问（requests.get() 调用需要它们）

我尝试了各种函数和类来完成此任务，但始终无法解决此问题。这是我能做到的最接近的：

class Api(object):
    def __init__(self, user=None, pswd=None):
        self.user = user
        self.pswd = pswd

    class Order(api):
        def __init__ (self, status=None):
            self.status = status

        @classmethod
        def get(cls, value):
            return cls(status=value)

        def create(self):
            auth = Auth(self.user, self.pswd) 
            # these credentials need to come from the Api() instance?, not self
            return x

        def update(self):
            auth = Auth(self.user, self.pswd) 
            # these credentials need to come from the Api() instance?, not self
            return x

这可能吗？还是我以错误的方式解决这个问题？我考虑过把它做成一个模块，但这似乎也不是一个有效的选择。

Answer 1

这演示了我认为您想要做的基本实现，我发现这比我在评论您的问题时想到的__get__、__set__hackery 更好

import requests

class Order:
    def __init__(self, user:str, passwd: str):
        self.session = requests.Session()
        self.session.auth = (user, passwd)
        self.status = None

    # This is only to make the class callable, since the class is
    # already instantiated in Api init calling it again would raise an exception
    def __call__(self, **kwargs):
        for key, value in kwargs.items():
            setattr(self, key, value)
        return self

    def get(self):
        response = self.session.get('https://httpbin.org/basic-auth/my_user/my_pass')
        print(response.text)

    def post(self):
        response = self.session.post('https://httpbin.org/post', data={'status': self.status})
        print(response.text)


class Api:
    def __init__(self, user: str, passwd: str):
        self.Order = Order(user, passwd)

Answer 2

Python 中的内部类只是单独的类，它们的实例不会以任何方式自动与外部类的实例关联。

我会建议一个解决方案，其中Order 的构造函数将Api 实例作为参数并使用该实例：

class Api(object):
    def __init__(self, user=None, pswd=None):
        self.user = user
        self.pswd = pswd

class Order(object):
    def __init__(self, api, status=None):
        self.api = api
        self.status = status

    @classmethod
    def get(cls, api, value):
        return cls(api, status=value)

    def create(self):
        auth = Auth(self.api.user, self.api.pswd)
        return x

    def update(self):
        auth = Auth(self.api.user, self.api.pswd)
        return x