如何在 Python 中创建包含类实例的对象？

Question

我想创建一个包含类的一些实例的对象。该对象应该是实例的某种列表泛化。例如，我有以下课程：class car:     def __init__(self, prize, color)         self.prize = prize         self.color = color现在我想要一个cars包含类汽车的许多实例的对象，但我可以像汽车实例一样使用它，即cars.prize应该返回我在该对象中收集的所有实例的奖品列表cars。

Answer 1

我认为你可以这样做：

class Cars:

    def __init__(self, list_of_cars):

        self.cars_list = list_of_cars

        self.prize = [car.prize for car in self.cars_list]

        self.color = [car.color for car in self.cars_list]

让我们看看如何使用它：

list_of_cars = [Car(1000, "red"), Car(2000, "blue"), Car(3000, "Green")]

x = Cars(list_of_cars)

print(x.prize)

# [1000, 2000, 3000]

print(x.color)

#["red", "blue", "Green"]

Answer 2

您可以创建一个class car_list()包含汽车列表的新列表（您可以向其添加、删除等）。在该类中，添加一个get_prizes()通过遍历列表返回奖品列表的方法。例如：

class car_list():

   def __init__(self, cars):

      self.cars = cars # This is a list

   def get_prizes(self):

      return [car.prize for car in self.cars]

Answer 3

代码中的小错误：您需要在方法定义行 :的末尾：__init__

def __init__(self, prize, color):

这是一个实现cars你想要的。装饰器的使用@property允许您将方法作为对象属性进行访问：

class car:

    def __init__(self, prize, color):

        self.prize = prize

        self.color = color

class cars:

    def __init__(self, list_of_cars):

        for one_car in list_of_cars:

            assert isinstance(one_car, car) # ensure you are only given cars

        self.my_cars = list_of_cars

    @property

    def prize(self):

        return [one_car.prize for one_car in self.my_cars]

    @property

    def color(self):

        return [one_car.color for one_car in self.my_cars]

>>> a = car('prize1', 'red')

>>> b = car('prize2', 'green')

>>> c = car('prize3', 'azure')

>>> carz = cars([a,b,c])

>>> carz.prize

['prize1', 'prize2', 'prize3']

>>> carz.color

['red', 'green', 'azure']

如果需要，您可以在每个对象中添加更多的输入检查，但这是基本框架。希望它有所帮助，快乐编码！

Answer 4

这个答案的灵感来自 Sam 使用装饰器的绝妙想法。因此，如果您认为自己对这段代码感到满意，请给他打分。

def singleton(all_cars):

    instances = {} # cars instances

    def get_instance():

        if all_cars not in instances:

            # all_cars is created once

            instances[all_cars] = all_cars()

        return instances[all_cars]

    return get_instance

@singleton

class all_cars:

    def __init__(self):

        self.inventory = {}

    @property

    def prizes(self):

        return [e.prize for e in self.inventory.values()]

    @property

    def colors(self):

        return [e.color for e in self.inventory.values()]        

class car:

    def __init__(self, prize, color):

        self.prize = prize

        self.color = color

    def register(self):

        # Like class all_cars is a singleton it is instantiate once, reason why dict is saved

        cars = all_cars()

        cars.inventory[len(cars.inventory)] = self

if __name__ == '__main__':

    # Creating cars items

    car1 = car("50", "Blue")

    car2 = car("300", "Red")

    car3 = car("150", "Gray")

    # Register part for cars

    car1.register()

    car2.register()

    car3.register()

    # Like class all_cars is a singleton it is instantiate once, reason why dict is saved

    cars = all_cars()

    print(cars.inventory)

    """{0: <__main__.car object at 0x7f3dbc469400>, ---> This is object car1

    1: <__main__.car object at 0x7f3dbc469518>,  ---> This is object car2

    2: <__main__.car object at 0x7f3dbc469550>}  ---> This is object car3"""

    print(cars.prizes)

    """['50', '300', '150']"""

    print(cars.colors)

    """['Blue', 'Red', 'Gray']"""