让一个类继承另一个类后，可以添加区分子类和父类所需的新属性和方法。
添加一个电动汽车特有的属性（电瓶），以及一个描述该属性的方法。
代码
# Hello World program in Python
# -- coding: utf-8 --
class Car(object):
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,mile):
self.odometer_reading+=miles
class ElectricCar(Car):
def __init__(self,make,model,year):
super(ElectricCar,self).__init__(make,model,year)
self.battery_size=70
def describe_battery(self):
print('This car has a '+str(self.battery_size)+' -kwh battery.')
my_tesla=ElectricCar('tesla','model s',2016)
print(my_tesla.get_descriptive_name())
my_tesla.describe_battery()
