Python 类

1. 第一个实例：

class Dog:
    """模拟小狗"""

    def __init__(self, name, 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("Will", 4)
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('Jim', 3)
print("\nYour dog's name is " + my_dog.name.title() + ".")
print("Your dog is " + str(my_dog.age) + " years old.")
my_dog.sit()
my_dog.roll_over()

2. 继承

# -*- coding: utf-8 -*-
# Created by: ZhaoDongshuang
# Created on: 18-1-26


class Car:
    """ 模拟汽车 """
    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, miles):
        self.odometer_reading += miles


class ElectricCar(Car):  # 继承时指定父类名称
    def __init__(self, make, model, year):
        """ 初始化父类 """
        super().__init__(make, model, year)
        """ 定义子类新属性 """
        self.battery_size = 70

    def describe_battery(self):
        """ 打印电瓶容量 """
        print("This car has a " + str(self.battery_size) + "-kWh battery.")


def test_electric_car():
    car_tesla = ElectricCar('tesla', 'model s', 2016)
    print(car_tesla.get_descriptive_name())
    car_tesla.describe_battery()

3. 将实例用作属性

class Car:
    """ 模拟汽车 """
    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, miles):
        self.odometer_reading += miles


class Battery:
    def __init__(self, battery_size=70):
        self.battery_size = battery_size

    def describe_battery(self):
        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 """
        drive_range = 300
        if self.battery_size == 70:
            drive_range = 240
        elif self.battery_size == 85:
            drive_range = 270
        message = "This car can go approximately " + str(drive_range) + \
                  " miles on a full charge."
        print(message)


class ElectricCar(Car):  # 继承时指定父类名称
    def __init__(self, make, model, year):
        """ 初始化父类 """
        super().__init__(make, model, year)
        """ 定义子类新属性 """
        self.battery = Battery()


def test_electric_car():
    car_tesla = ElectricCar('tesla', 'model s', 2016)
    print(car_tesla.get_descriptive_name())
    car_tesla.battery.describe_battery()

4. 从一个模块中导入多个类

from car import Car, ElectricCar

5. 导入整个模块

import car

6. 导入模块中的所有类

from module_name import *

7. 类编码风格建议

• 类名应采用驼峰命名法，即将类名中的每个单词的首字母都大写，而不使用下划线。实例名和模块名都采用小写格式，并在单词之间加上下划线。
• 对于每个类，都应紧跟在类定义后面包含一个文档字符串。这种文档字符串简要地描述类的功能，并遵循编写函数的文档字符串时采用的格式约定。每个模块也都应包含一个文档字符串，对其中的类可用于做什么进行描述。
• 可使用空行来组织代码,但不要滥用。在类中，可使用一个空行来分隔方法；而在模块中，可使用两个空行来分隔类。
• 需要同时导入标准库中的模块和你编写的模块时，先编写导入标准库模块的 import 语句，再添加一个空行，然后编写导入你自己编写的模块的 import 语句。在包含多条 import 语句的程序中，这种做法让人更容易明白程序使用的各个模块都来自何方。

本文参考自 《Python 编程：从入门到实践》