# oop/class_inheritance.py
class Engine:
    def start(self):
        pass

    def stop(self):
        pass

class ElectricEngine(Engine):  # Is-A Engine
    pass

class V8Engine(Engine):  # Is-A Engine
    pass

class Car:
    engine_cls = Engine

    def __init__(self):
        self.engine = self.engine_cls()  # Has-A Engine

    def start(self):
        print(
            'Starting engine {0} for car {1}... Wroom, wroom!'
            .format(
                self.engine.__class__.__name__,
                self.__class__.__name__)
        )
        self.engine.start()

    def stop(self):
        self.engine.stop()

class RaceCar(Car):  # Is-A Car
    engine_cls = V8Engine

class CityCar(Car):  # Is-A Car
    engine_cls = ElectricEngine

class F1Car(RaceCar):  # Is-A RaceCar and also Is-A Car
    pass  # engine_cls same as parent

car = Car()
racecar = RaceCar()
citycar = CityCar()
f1car = F1Car()
cars = [car, racecar, citycar, f1car]

for car in cars:
    car.start()

"""
$ python class_inheritance.py
Starting engine Engine for car Car... Wroom, wroom!
Starting engine V8Engine for car RaceCar... Wroom, wroom!
Starting engine ElectricEngine for car CityCar... Wroom, wroom!
Starting engine V8Engine for car F1Car... Wroom, wroom!
"""