オブジェクト指向

class Person(object):
    def __init__(self, age=1):
        self.age = age
    def drive(self):
        if self.age >= 18:
            print('OK')
        else:
            raise Exception('No drive')

class Baby(Person):
    def __init__(self, age=1):
        if age < 18:
            super().__init__(age)
        else:
            raise ValueError

class Adult(Person):
    def __init__(self, age=18):
        if age >= 18:
            super().__init__(age)
        else:
            raise ValueError

class Car(object):
    def __init__(self, model=None):
        self.model = model
    def run(self):
        print('run')
    def ride(self, person):
        person.drive()

baby = Baby()
adult = Adult()
car = Car()

car.ride(adult)

実行結果

OK

最後の行を

car.ride(baby)

にかえると

実行結果

Exception: No drive