python实例传递到属性中修改实例中包含的属性

Question

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 = f"{self.year} {self.make} {self.model}"
        return long_name.title()

    def read_odometer(self):

        print(f"This car has {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 on odometer!")
    def increment_odometer(self, miles):
        self.odometer_reading += miles

class Battery:
    def __init__(self, battery_size=75):
        self.battery_size = battery_size

    def describe_battery(self):
        print(f"This car has a {self.battery_size}-kWh battery.")


class ElectricCar(Car):

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


my_tesla = ElectricCar('tesla', 'model s', 2019)
print(my_tesla.get_descriptive_name())
my_tesla.battery.describe_battery()

如果要在最后输出的my_tesla.battery.describe_battery()不显示默认值，而是更改后的参数值，该怎样去传入新的Battery类中包含的battery_size参数呢？我个人思路是在Battery类中新增一个修改的参数用的方法，在最后输出前执行一下修改的方法，再执行最后的输出结果，不知道这样正确不？

Answer 1

你的思路是可以的，如果battery_size是需要频繁修改的话就增加一个修改的方法，如果一开始实例化 ElectricCar的时候就是固定不变的话，可以直接初始化self.battery = Battery(battery_size)。

另一种思路就是采用多继承：

class ElectricCar(Car, Battery):
    def __init__(self, make, model, year, battery_size=75):
        Car.__init__(self, make, model, year)
        Battery.__init__(self, battery_size)