Python基础-9.2 使用类和实例

9.2.1 Car类

class Car():
    """一次模拟汽车的简单尝试"""
    def __init__(self, make, model, year):  # 注意__inint__下划线是左右两边各两个，若出错会报出takes no arguments的错误
        """初始化描述汽车的属性"""
        self.make = make
        self.model = model
        self.year = year

    def get_descriptive_name(self):
        """返回整洁的描述信息"""
        long_name = str(self.year) + " " + self.make + ' ' + self.model
        print(long_name.title())
my_new_car = Car('audi', 'a4', 2006)
my_new_car.get_descriptive_name()

①注意__init__函数的下划线为左右各两个，有误会报TypeError: Car() takes no arguments

9.2.2 给属性指定默认值

class Car():
    """一次模拟汽车的简单尝试"""
    def __init__(self, make, model, year):  # 注意__inint__下划线是左右两边各两个，若出错会报出takes no arguments的错误
        """初始化描述汽车的属性"""
        self.make = make
        self.model = model
        self.year = year
        # 添加odometer_reading属性，使其初始值为0
        self.odometer_reading = 0

    def get_descriptive_name(self):
        """返回整洁的描述信息"""
        long_name = str(self.year) + " " + self.make + ' ' + self.model
        print(long_name.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.")

        
my_new_car = Car('audi', 'a4', 2006)
my_new_car.get_descriptive_name()
my_new_car.read_odometer()

9.2.3 修改属性的值

1.直接修改:用句点表示法直接访问并设置汽车属性odometer_reading

my_new_car.odometer_reading = 222
my_new_car.read_odometer()

2.通过方法修改属性的值：无需直接访问属性，将值传递给一个方法，由它在内部更新

ef update_odometer(self, mileage):
"""将里程表读数设置为指定的值"""
self.odometer_reading = mileage

my_new_car.odometer_reading = 222

.添加禁止任何人将里程表往回调的逻辑：大于或等于原来的里程，就将数据改为新指定的；否则发出警告。

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 !")

3.同过方法对属性的值进行递增

def increment_odometer(self, miles):
    """
    将里程表读数增加指定的量
    禁止增加量为负数
    """
    if miles >= 0:
        self.odometer_reading += miles
    else:
        print("You can't add negative number on  odometer !")

小结：

class Car():
    """一次模拟汽车的简单尝试"""
    def __init__(self, make, model, year):  # 注意__inint__下划线是左右两边各两个，若出错会报出takes no arguments的错误
        """初始化描述汽车的属性"""
        self.make = make
        self.model = model
        self.year = year
        # 添加odometer_reading属性，使其初始值为0
        self.odometer_reading = 20

    def get_descriptive_name(self):
        """返回整洁的描述信息"""
        long_name = str(self.year) + " " + self.make + ' ' + self.model
        print(long_name.title())

    def update_odometer(self, mileage):
        """将里程表读数设置为指定的值"""
        # self.odometer_reading = 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量
        禁止增加量为负数
        """
        if miles >= 0:
            self.odometer_reading += miles
        else:
            print("You can't add negative number on  odometer !")

    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.")


my_new_car = Car('audi', 'a4', 2006)
my_new_car.get_descriptive_name()
# my_new_car.odometer_reading = 222
my_new_car.update_odometer(30)
my_new_car.read_odometer()

my_new_car.increment_odometer(100)
my_new_car.read_odometer()

练习：

9-4

# 9-4
class Restaurant():
    def __init__(self, restaurant_name, cuisine_type):
        self.name = restaurant_name
        self.type = cuisine_type
        self.number_served = 0

    def set_number_served(self, num):
        """设置就餐人数"""
        self.number_served = num

    def increment_number_served(self, add_num):
        """增加就餐人数"""
        self.number_served += add_num

    def describe_restaurant(self):
        print("\nThe restaurant's name is " + self.name.title() + "!")
        print("\nThe restaurant is " + self.type + "!")
        print("\n There are " + str(self.number_served) + " people be served")

    def open_restaurant(self):
        print("\n" + self.name.title() + " is open !")


restaurant_1 = Restaurant('紫光阁', '川菜馆')
restaurant_1.open_restaurant()
restaurant_1.set_number_served(7)
restaurant_1.increment_number_served(3)
restaurant_1.describe_restaurant()
9-5

# 9-5
class User():
    def __init__(self, first_name, last_name):
        self.first_name = first_name
        self.Last_name = last_name
        self.login_attempts = 0

    def increment_login_attempts(self):
        self.login_attempts += 1

    def reset_login_attempts(self):
        self.login_attempts = 0


    def describe_user(self):
        """"打印客户信息"""
        print("\nThe user's name is " + self.first_name.title() + " " + self.Last_name + "!")
        print("Login attempts is " + str(self.login_attempts))

    def greet_user(self):
        """向用户发出个性化问候"""
        name = self.first_name.title() + " " + self.Last_name
        print("Hello, " + name)


user1 = User('lily', 'jhon')
user1.increment_login_attempts()
user1.increment_login_attempts()
user1.increment_login_attempts()
user1.reset_login_attempts()
user1.describe_user()