第九章（python编程从入门到实践）

9-7 管理员：

管理员是一种特殊的用户。编写一个名为Admin 的类，让它继承你为完成练习 9-3或练习 9-5而编写的User 类。添加一个名为privileges 的属性，用
于存储一个由字符串（如" can add post" 、 " can delete post" 、 " can ban user" 等）组成的列表。编写一个名为show_privileges( ) 的方法，它
显示管理员的权限。创建一个Admin 实例，并调用这个方法。

class User():
    
    def __init__(self,first_name,last_name):
        self.first_name = first_name
        self.last_name = last_name
        
    def describe_user(self):
        print("\nFull name is " +self.first_name.title() + ' ' +
              self.last_name.title())
        
    def greet_user(self):
        print("Hello," + self.first_name.title() + ' ' +
              self.last_name.title() + '!' )
        
class Admin(User):
    
    def __init__(self,first_name,last_name):
        super().__init__(first_name,last_name)
        self.privileges = ['can add post','can delete post','can ban user']
        
    def show_privileges(self):
        print(self.first_name.title() + ' ' + self.last_name.title() + ' ' +
              self.privileges[0] + '.')
        
admin_1 = Admin('wang','wei')
admin_1.show_privileges()

9-8 权限：编写一个名为Privileges 的类，它只有一个属性——privileges ，其中存储了练习9-7 所说的字符串列表。将方法show_privileges( ) 移到这
个类中。在Admin 类中，将一个Privileges 实例用作其属性。创建一个Admin 实例，并使用方法show_privileges( ) 来显示其权限。

class User():
    
    def __init__(self,first_name,last_name):
        self.first_name = first_name
        self.last_name = last_name
        
    def describe_user(self):
        print("\nFull name is " +self.first_name.title() + ' ' +
              self.last_name.title())
        
    def greet_user(self):
        print("Hello," + self.first_name.title() + ' ' +
              self.last_name.title() + '!' )

class Privileges():
    
    privileges = ['can add post','can delete post','can ban user']
        
    def show_privileges(self):
            print(self.privileges)
            
class Admin(User):
    
    def __init__(self,first_name,last_name):
        super().__init__(first_name,last_name)
        self.privilege = Privileges()

admin_1 = Admin('wang','wei')
admin_1.privilege.show_privileges()

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。

class Car():
    """一次模拟汽车的简单尝试"""
    
    def __init__(self,make,model,year):
        """初始化描述汽车的属性"""
        self.make = make
        self.model = model
        self.year = year
        self.odometer_reading = 0
        
    def get_descriptive_name(self):
        """返回整洁的描述性信息"""
        long_time = str(self.year) + ' ' + self.make + ' ' +self.model
        return long_time.title()
    
    def read_odometer(self):
        """打印一条指出汽车里程的消息"""
        print("This car has " + str(self.odometer_reading) + " miles on it.")
        
    def update_odometer(self,mileage):
        """将里程表读数设置为指定的值
        禁止将里程表读数往回调
        """
        if mileage >= self.odometer_reading:
            self.odometer_reading = mileage
        else:
            print("You can't roll back an odometer!")
            
    def increment_odometer(self,miles):
        """将里程表读数增加指定的值"""
        self.odometer_reading += miles
        
    def fill_gas_tank(self):
        print("come on!")
        
class Battery():
    """一次模拟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):
        
        if self.battery_size != 85:
            self.battery_size = 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"""
        super().__init__(make,model,year)
        self.battery = Battery()
               
    def fill_gas_tank(self):
        print("This car doesn't need a gas tank!")
        
my_tesla = ElectricCar('tesla','model s',2016)
print(my_tesla.get_descriptive_name())
my_tesla.battery.describe_battery()
my_tesla.battery.get_range()

my_tesla.battery.upgrade_battery()
my_tesla.battery.get_range()

第九章（python编程从入门到实践）

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