9.3.6　模拟实物
模拟较复杂的物件（如电动汽车）时，需要解决一些有趣的问题。续航里程是电瓶的属性还是汽车的属性呢？如果我们只需描述一辆汽车，那么将方法get_range() 放在Battery 类中也许是合适的；但如果要描述一家汽车制造商的整个产品线，也许应该将方法get_range() 移到ElectricCar 类中。在这种情况下，get_range() 依然根据电瓶容量来确定续航里程，但报告的是一款汽车的续航里程。我们也可以这样做：将方法get_range() 还留在Battery 类中，但向它传递一个参数，如car_model ；在这种情况下，方法get_range() 将根据电瓶容量和汽车型号报告续航里程。
该怎么写呢？

class Car():
    def __init__(self,make,model,year):
        self.make = make
        self.model = model
        self.year = year
        self.odometer_reading = 100
    def describe(self):
       long_name = str(self.year) + ' ' + self.make + ' ' + self.model
       return long_name.title()
    def read_odometer(self):
        print("this car has " + str(self.odometer_reading) + " miles on it.")
    def update_odometer(self,mileage):
        if mileage >=self.odometer_reading:
            self.odometer_reading = mileage
        else:
            print("you can't roll back an odometer!")
    def increment(self,miles):
        self.odometer_reading = self.odometer_reading + miles
my_new_car = Car('audi','a4','2016')
print(my_new_car.describe())

#电动车类
class Battery():
    def __init__(self,battery_size=70):
        self.battery_size = battery_size

    def describe_battery(self):
        print("this car has a " + str(self.battery_size) + "-kwh battery")

    def get_range(self):
        if self.battery_size == 70:
            range = 240

        message = "this car can go approximately " + str(range)
        message += " miles on a full charge."
        print(message)

class ElectricCar(Car):
    def __init__(self,make,model,year):
        super(ElectricCar, self).__init__(make,model,year)
        self.battery = Battery()

my_tesla = ElectricCar('tesla','model s',2016)
print(my_tesla.describe())
my_tesla.battery.describe_battery()
my_tesla.battery.get_range()

class Car(object):这样才行，不然不能运行

# -*- coding: UTF-8 -*-

class Car(object):
    def __init__(self,make,model,year):
        self.make = make
        self.model = model
        self.year = year
        self.odometer_reading = 100
    def describe(self):
       long_name = str(self.year) + ' ' + self.make + ' ' + self.model
       return long_name.title()
    def read_odometer(self):
        print("this car has " + str(self.odometer_reading) + " miles on it.")
    def update_odometer(self,mileage):
        if mileage >=self.odometer_reading:
            self.odometer_reading = mileage
        else:
            print("you can't roll back an odometer!")
    def increment(self,miles):
        self.odometer_reading = self.odometer_reading + miles
my_new_car = Car('audi','a4','2016')
print(my_new_car.describe())

class Battery():
    def __init__(self,battery_size=70, car_model="model s"):
        self.battery_size = battery_size
        self.car_model = car_model

    def describe_battery(self):
        print("this car has a " + str(self.battery_size) + "-kwh battery")

    #这里修改
    def get_range(self):
        if self.battery_size == 70 and self.car_model == "model s":
            range = 240
        elif self.battery_size == 70 and self.car_model == "model 3":
            range = 120         

        message = self.car_model  + " can go approximately " + str(range)
        message += " miles on a full charge."
        print(message)

#电动车类
class ElectricCar(Car):
    def __init__(self,make,model,year):
        super(ElectricCar, self).__init__(make,model,year)
        #这里修改
        self.battery = Battery(70, model)

my_tesla = ElectricCar('tesla','model s',2016)
print(my_tesla.describe())
my_tesla.battery.describe_battery()
my_tesla.battery.get_range()

2016 Audi A4
2016 Tesla Model S
this car has a 70-kwh battery
model s can go approximately 240 miles on a full charge.

问题解决的话，请点下采纳。