[Python知识库]Python编程从入门到实践 课后题 9-9电瓶升级

在本节最后一个electric_car.py版本中，给Battery 类添加一个名为upgrade_battery() 的方法。这个方法检查电瓶容量，如果它不是85，就将它 设置为85。创建一辆电瓶容量为默认值的电动汽车，调用方法get_range() ，然后对电瓶进行升级，并再次调用get_range() 。你会看到这辆汽车的续航里程增加了。
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#electric_car.py 最终版本
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): #车的名字
        long_name = str(self.year) + ' ' + self.make + ' ' + self.model
        return long_name.title()
    def read_odometer(self): #读公里数
        print("This car has " + str(self.odometer_reading) + ' miles on it.')
    def update_odometer(self, mileage): #给公里数赋值，且不允许自己往回调公里数
        if mileage >= self.odometer_reading:
            self.odometer_reading = mileage
        else:
            print("You can't roll back an odometer!!")
    def increment_odometer(self , miles): #公里数增加指定的量
        self.odometer_reading += miles

class Battery():
    def __init__(self , battery_size = 70): #初始化电瓶的属性
        self.battery_size = battery_size
    def describe_battery(self): #打印电瓶容量
        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 = 270
        message = "This car can go approximately " + str(range)
        message += " miles on a full charge."
        print(message)

        #9-9新添加的方法
    def upgrade_battery(self):
        if self.battery_size != 85:
            self.battery_size = 85


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

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

print('\n------')
my_tesla.battery.upgrade_battery()
my_tesla.battery.get_range()

结果

2016 Tesla Model S
This car has a 70-KWH battery.
This car can go approximately 240 miles on a full charge.

------
This car can go approximately 270 miles on a full charge.

Process finished with exit code 0