Python编程：从入门到实践—类

创建类

#!/usr/bin/env python
# --*-- encoding:utf-8 --*--

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):
        """模拟小狗别命令时蹲下"""
        print(self.name.title() + " is now sitting.")
    def roll_over(self):
        """模拟小狗被命中时打滚"""
        print(self.name.title() + " rolled over!")

my_dog = Dog('willie',6)

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

my_dog.sit()

print("\nYour dog's name is " + your_dog.name.title() + ".")
print("Your dog is " + str(your_dog.age) + " years old.")

your_dog.sit()

给属性指定默认值

#!/usr/bin/env python
# --*-- encoding:utf-8 --*--

class Car():
    def __init__(self,make,model,year):
        """模拟汽车的的属性"""
        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_name = str(self.year) + ' ' + self.make + ' ' + self.model
        return 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','a3',2016)

print(my_new_car.get_descriptive_name())

my_new_car.read_odometer()

修改属性的值：
1：直接修改属性的值

#!/usr/bin/env python
# --*-- encoding:utf-8 --*--

class Car():
    def __init__(self,make,model,year):
        """模拟汽车的的属性"""
        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_name = str(self.year) + ' ' + self.make + ' ' + self.model
        return 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','a3',2016)

print(my_new_car.get_descriptive_name())
my_new_car.odometer_reading = 23
my_new_car.read_odometer()

直接修改属性的值

2：通过方法修改属性的值

#!/usr/bin/env python
# --*-- encoding:utf-8 --*--
class Car():
    def __init__(self,make,model,year):
        """模拟汽车的的属性"""
        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_name = str(self.year) + ' ' + self.make + ' ' + self.model
        return 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.")
    def update_odometer(self,mileage):
        """将里程表读书设置为指定的值"""
        self.odometer_reading = mileage

my_new_car = Car('audi','a3',2016)
print(my_new_car.get_descriptive_name())

my_new_car.update_odometer(23)

my_new_car.read_odometer()

通过方法修改属性值

#!/usr/bin/env python
# --*-- encoding:utf-8 --*--
class Car():
    def __init__(self,make,model,year):
        """模拟汽车的的属性"""
        self.make = make
        self.model = model
        self.year = year
        self.odometer_reading = 25
    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!")

my_new_car = Car('audi','a3',2016)
print(my_new_car.get_descriptive_name())

my_new_car.update_odometer(23)

my_new_car.read_odometer()

执行结果：
2016 Audi A3
You can't roll back an odometer!
This car has 25 miles on it.

扩展

3：通过方法对属性的值进行递增

继承

如果编写的类是另一个现成类的特殊版本，可使用继承。一个类集成另一个类时，它将自动获得另一个类的所有属性和方法；原有的类称为父类，而新类称为子类。

子类继承了其父类的所有属性和方法，同时还可以定义自己的属性和方法。