9-9 电瓶升级

1. 项目

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。

2. 代码

class Car():
    """一次模拟汽车的简单尝试"""
    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't roll back an odometer!")

    def increment_odometer(self, miles):
        self.odometer_reading += miles

class Battery():
    """一次模拟电动汽车电瓶的简单尝试"""
    def __init__(self, battery_size = 70):
        """初始化电瓶的属性"""
        self.battery_size = battery_size

    def describe_battery(self):
        """打印一条描述电瓶容量的消息"""
        print("This car has a " + str(self.battery_size) + "-kWh battery.")

    def get_range(self):
        """打印一条消息，指出电瓶的续航里程"""
        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)

    def upgrade_battery(self):  # 添加方法
            self.battery_size = 85  # 设置电瓶大小为85

class ElectricCar(Car):
    """电动汽车的独特之处"""
    def __init__(self, make, model, year):
        """初始化父类的属性，再初始化电动汽车特有的属性"""
        super().__init__(make, model, year)
        self.battery = Battery() # 把电瓶类作为电瓶车的属性

my_BYD = ElectricCar('BYD', '秦', 2012)  # 创建默认值电瓶容量的车
my_BYD.battery.get_range()      # 调用电瓶的方法
my_BYD.battery.upgrade_battery() # 调用电瓶的方法
my_BYD.battery.get_range()

　　

3. 运行结果

D:\python编程：从入门到实践\venv\Scripts\python.exe "D:/python编程：从入门到实践/9-9 电瓶升级.py"
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