vehicles.py

class Vehicle:
    def __init__(self, make, year):
        self._make = make
        self._year = year

    @property
    def make(self):
        return self._make

    @make.setter
    def make(self, value):
        self._make = value

    @property
    def year(self):
        return self._year

    @year.setter
    def year(self, value):
        if not Vehicle.is_valid_year(value):
            raise ValueError("Invalid year.")
        self._year = value

    def __str__(self):
        return f"{self.year} {self.make}"

    @staticmethod
    def is_valid_year(y):
        return 1900 <= y <= 2026


class Car(Vehicle):
    def __init__(self, make, year, doors=4):
        super().__init__(make, year)
        self._doors = doors

    @property
    def doors(self):
        return self._doors

    @doors.setter
    def doors(self, value):
        self._doors = value

    def __str__(self):
        return f"Car: {self.year} {self.make}, {self.doors} doors"


class Bicycle(Vehicle):
    def __init__(self, make, year, gears=1):
        super().__init__(make, year)
        self._gears = gears

    @property
    def gears(self):
        return self._gears

    @gears.setter
    def gears(self, value):
        self._gears = value

    def __str__(self):
        return f"Bicycle: {self.year} {self.make}, {self.gears} gears"


# --- demo ---
car = Car("Toyota", 2020, doors=4)
bike = Bicycle("Trek", 2022, gears=21)

print(car)
print(bike)

car.doors = 2
bike.gears = 18

print(car)
print(bike)
print("Valid year 1800?", Vehicle.is_valid_year(1800))