Builder Pattern in Python

builder.py

class VehicleDirector:
    __builder = None

    def set_builder(self, builder):
        self.__builder = builder

    def build(self):
        vehicle = Vehicle()

        vehicle.set_body(self.__builder.get_body())
        vehicle.set_engine(self.__builder.get_engine())
        for tires in range(self.__builder.get_tires_number()):
            vehicle.attach_wheel(self.__builder.get_wheel())

        return vehicle


class Vehicle:
    def __init__(self):
        self.__wheels = list()
        self.__engine = None
        self.__body = None

    def set_body(self, body): self.__body = body

    def set_engine(self, engine): self.__engine = engine

    def attach_wheel(self, wheel): self.__wheels.append(wheel)

    def specifications(self):
        print('Body: {}'.format(self.__body.shape))
        print('Engine HorsePower: {}'.format(self.__engine.horsepower))
        print('Tires:')
        print('\tNumber: {}'.format(len(self.__wheels)))
        print('\tSize: {}'.format(self.__wheels[0].size))


class Builder:
    def get_body(self): raise(NotImplementedError)

    def get_engine(self): raise(NotImplementedError)

    def get_wheel(self): raise(NotImplementedError)

    def get_tires_number(self): return 0


class BMWBuilder(Builder):
    def get_body(self): return Body(shape='compact executive')

    def get_engine(self): return Engine(horsepower=400)

    def get_wheel(self): return Wheel(size=22)

    def get_tires_number(self): return 4


class MotorcycleBuilder(Builder):
    def get_body(self): return Body(shape='sport')

    def get_engine(self): return Engine(horsepower=250)

    def get_wheel(self): return Wheel(size=18)

    def get_tires_number(self): return 2


class Engine:
    def __init__(self, horsepower): self.horsepower = horsepower


class Wheel:
    def __init__(self, size): self.size = size


class Body:
    def __init__(self, shape): self.shape = shape


bmw_builder = BMWBuilder()
bike_builder = MotorcycleBuilder()

director = VehicleDirector()

print('BMW')
director.set_builder(bmw_builder)
bmw = director.build()
bmw.specifications()

print('Bike')
director.set_builder(bike_builder)
bike = director.build()
bike.specifications()