如何将类实例分配给变量并在其他类中使用它 [英] how to assign Class Instance to a variable and use that in other class

问题描述

我正在为 Python 做一些基本的练习.在这里，我定义了 3 个类.现在，我需要在另一个类中传递第一个类的实例并在最后一个类中使用它.

I am doing some basic practice for Python. Here, I am defining 3 classes. Now, I need to pass instance of first class in another class and use that in the last one.

我写的代码如下:

#defining first class:
class MobileInventory:

    def __init__(self, inventory=None):
        if inventory == None:
            balance_inventory = {}
        elif not isinstance(inventory, dict):
            raise TypeError("Input inventory must be a dictionary")
        elif not (set(map(type, inventory)) == {str}):
            raise ValueError("Mobile model name must be a string")
        elif [True for i in inventory.values() if (not isinstance(i, int) or i < 1)]:
            raise ValueError("No. of mobiles must be a positive integer")
        self.balance_inventory = inventory

# class to add elements to existing dictionary of above class
class add_stock:

    def __init__(self, m, new_stock):
        if not isinstance(new_stock, dict):
            raise TypeError("Input stock must be a dictionary")
        elif not (set(map(type, new_stock)) == {str}):
            raise ValueError("Mobile model name must be a string")
        elif [True for i in new_stock.values() if (not isinstance(i, int) or i < 1)]:
            raise ValueError("No. of mobiles must be a positive integer")

        for key, value in new_stock.items():
            if key in m.balance_inventory.keys():
                x = m.balance_inventory[key] + value
                m.balance_inventory[key] = x
            else:
                m.balance_inventory.update({key: value})

#class to testing the above functionality
class Test_Inventory_Add_Stock:

    m = ''

    def setup_class():
        m = MobileInventory({'iPhone Model xy': 100, 'Xiaomi Model YA': 1000, 'Nokia Model Zs': 25})
        print(m.balance_inventory)  # giving Output {'iPhone Model xy': 100, 'Xiaomi Model YA': 1000, 'Nokia Model Zs': 25}

    def test_add_new_stock_as_dict():
        add_stock( m, {'iPhone Model X': 50, 'Xiaomi Model Y': 2000, 'Nokia Model A': 10})

Test_Inventory_Add_Stock.setup_class()
Test_Inventory_Add_Stock.test_add_new_stock_as_dict()

上面我为 test_add_new_stock_as_dict 方法给出了错误 'NameError: name 'm' is not defined'.

The above i giving error 'NameError: name 'm' is not defined' for test_add_new_stock_as_dict method.

当我在课堂上宣布时，为什么不采取 m?如何在 add_stock 类中直接使用 MobileInventory.balance_inventory?我试过它给出了错误.

Why is it not taking m, when I am declaring that in class? how is it possible to use MobileInventory.balance_inventory directly in add_stock class? I tried it's giving error.

预期:我需要删除 NameError.以及在没有实例的情况下直接在类中使用 MobileInventory.balance_inventory(即另一个类引用)的任何方式

Expected: I need to remove the NameError. And any way to use MobileInventory.balance_inventory (i.e. another class reference) directly in class without instance of that

推荐答案

Python 变量名作用域更喜欢局部作用域而不是外部作用域，因此您需要告诉解释器 m 来自何处.

Python variable name scopes prefer the local scope over anything outside, so you need to tell the interpreter where m is coming from.

在第一种和第二种方法中，您都可以使用 Test_Inventory_Add_Stock.m 来引用您的静态类变量 m.

Both in the first and second method, you can use Test_Inventory_Add_Stock.m to refer to your static class variable m.

class Test_Inventory_Add_Stock:

    m = ''

    def setup_class():
        Test_Inventory_Add_Stock.m = MobileInventory({'iPhone Model xy': 100, 'Xiaomi Model YA': 1000, 'Nokia Model Zs': 25})
        print(m.balance_inventory)  # giving Output {'iPhone Model xy': 100, 'Xiaomi Model YA': 1000, 'Nokia Model Zs': 25}

    def test_add_new_stock_as_dict():
        add_stock(Test_Inventory_Add_Stock.m, {'iPhone Model X': 50, 'Xiaomi Model Y': 2000, 'Nokia Model A': 10})

但这看起来不太好.要将变量限制在类的实例中，请尝试以下操作:

But that doesn't look very good. To keep the variables confined to an instance of the class, try this:

class Test_Inventory_Add_Stock:

    def setup_class(self):
        self.m = MobileInventory({'iPhone Model xy': 100, 'Xiaomi Model YA': 1000, 'Nokia Model Zs': 25})
        print(m.balance_inventory)  # giving Output {'iPhone Model xy': 100, 'Xiaomi Model YA': 1000, 'Nokia Model Zs': 25}

    def test_add_new_stock_as_dict(self):
        add_stock(self.m, {'iPhone Model X': 50, 'Xiaomi Model Y': 2000, 'Nokia Model A': 10})

t = Test_Inventory_Add_Stock()
t.setup_class()
t.test_add_new_stock_as_dict()

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