在python中编写一个简单的关于类的情况遇到的问题（待解决）

car.py


class Car():
    def __init__(self, make, model, year):
        self.make = make
        self.model = model
        self.year = year
        self.odometer_reading = 0
    def get_descriptive_name(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 not roll back an odometer!")
    def increment_odometer(self, miles):
        self.odometer_reading += miles
class Battry():
    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
        elif self.battery_size == 85:
            range = 999
        message = "This car go approximately " + str(range)
        message += " miles on a full charge."
        print(message)

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

my_tesla = ElectircCar(‘tesla‘,‘model s‘,2016)
print(my_tesla.get_descriptive_name())
my_tesla.battery.describe_battery()
my_tesla.battery.get_range()
print("i am just for a test")

my_car.py

from car import Car
my_new_car = Car(‘audi‘,‘a4‘,2016)
print(my_new_car.get_descriptive_name())
my_new_car.odometer_reading = 23
my_new_car.read_odometer()