python入门-类(一)

1 最简单的一个类

class Dog():
    """一次模拟小狗的简单尝试"""
    def __init__(self,name,age):
        """初始化属性name和age"""
        self.name = name
        self.age = age

    def sit(self):
        print(self.name.title() + " is now sitting.")

    def roll_over(self):
        print(self.name.title() + " rolled over")


my_dog = Dog('willie',6)
print("My dog's name is " + my_dog.name.title() + ".")
print("My dog is " + str(my_dog.age) + "years old.")

my_dog.sit()
my_dog.roll_over()

__init__是初始化类

类的属性和方法的 访问方式  默认的self 是自身，函数可以编写这个形参，但是实际不用传self

2 一个类 可以创建多个实例

class Dog():
    """一次模拟小狗的简单尝试"""
    def __init__(self,name,age):
        """初始化属性name和age"""
        self.name = name
        self.age = age

    def sit(self):
        print(self.name.title() + " is now sitting.")

    def roll_over(self):
        print(self.name.title() + " rolled over")


my_dog = Dog('willie',6)
print("My dog's name is " + my_dog.name.title() + ".")
print("My dog is " + str(my_dog.age) + "years old.")

my_dog.sit()
my_dog.roll_over()

your_dog = Dog('lucy',3)
print("Your dog's name is " + your_dog.name.title() + ".")
print("Your dog is " + str(your_dog.age) + "years old.")

3 类的多个用法

class Car():
    """一次模拟汽车的简单尝试"""
    def __init__(self,make,model,year):
        """初始化属性"""
        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_name = str(self.year) + " " + self.make + '' + self.model
        return long_name.title()

    def read_odometer(self):
        """打印汽车里程的信息"""
        print("This car has " + str(self.odometer_reading) + "miles on it")

    def update_odometer(self,mileage):
        self.odometer_reading = mileage

    def increment_odometer(self,miles):
        self.odometer_reading += miles

    def fill_gas_tank(self):
        print("This car doesn't need a gas tank")

my_new_car = Car('audi', 'a4' ,'2016')
print(my_new_car.get_descriptive_name())
my_new_car.read_odometer()

my_new_car.odometer_reading=23
my_new_car.read_odometer()

my_new_car.update_odometer(36)
my_new_car.read_odometer()

my_new_car.increment_odometer(100)
my_new_car.read_odometer()

可以给类添加默认值，也可以修改类中的属性的值 多重练习

4 类的继承

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_size = 70

    def describe_battery(self):
        print("This car has a " + str(self.battery_size) +"-kwh battery.")

    def fill_gas_tank(self):
        print("This is OK!")

my_tesla = ElectricCar('tesla','model s',2016)
print(my_tesla.get_descriptive_name())
my_tesla.describe_battery()
my_tesla.fill_gas_tank()

紧跟着上面，创建一个子类，可以在子类中复写父类的方法

子类和父类使用关键字super()关联   父类也叫做超类，这是super的由来

5  把类集中放到 其他的类中，也可以方便的调用

class Battery():
    def __init__(self,battery_size=70):
        """初始化电瓶的属性"""
        self.battery_size = battery_size

    def describe_battery(self):
        """打印一天描述电瓶容量的消息"""
        print("This car has a " +str(self.battery_size) + "-kwh battery.")

    def get_range(self):
        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)

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()



my_tesla = ElectricCar('tesla','model s',2016)
print(my_tesla.get_descriptive_name())
my_tesla.battery.describe_battery()
my_tesla.battery.get_range()