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

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

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

?

1 2 3 4 5

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