How can I create an object that contains instances of a class in Python?

I think you can do something like that:

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]

Let's see how it can be used:

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"]

You could create a new class car_list() that holds a list of cars (to which you can append, remove etc). In that class, add aget_prizes() method that returns a list of prizes by iterating over the list. For example:

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]

Small error in your code: you need a : at the end of your __init__ method definition line:
def __init__(self, prize, color):

Here's an implementation of cars which does what you desire. The use of the @property decorator allows you to access methods as object properties:

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']

You can add more checking on inputs in each object if desired, but this is the basic framework. Hope it helps, Happy Coding!

This answer is inspired by the wonderful Sam idea of using decorators. So please give him the point if you think you are pleased with this chunk of code.

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']"""