一、类的基础操作

1. 创建和使用类：

  1. # 首先我们先创建一个名为 Dog 的类（python中首字母大写的名字为类名）
  2. class Dog():
  3.     """A simple attempt to model a dog.""" # 文档字符串注释
  5.     # _init_()方法比较特殊，创建新实例时会自动运行 （def后面的名为“方法”）
  6.     # 在方法定义中self形参必不可少，python会自动传入self实参，我们不用管
  7.     def __init__(self, name, age):
  8.         """Initialize name and age attributes."""
  9.         self.name = name # 以self为前缀的变量可供类中的所有方法使用
  10.         self.age = age 
  12.     def sit(self):
  13.         """Simulate a dog sitting in response to a command."""
  14.         print(self.name.title() + " is now sitting.")
  16.     def roll_over(self):
  17.         """Simulate rolling over in response to a command."""
  18.         print(self.name.title() + " rolled over!")
  20. # 创建两个实例
  21. my_dog = Dog('willie', 6)
  22. your_dog = Dog('lucy', 3)
  23. # 用 句点法 访问属性
  24. print("My dog's name is " + my_dog.name.title() + ".")
  25. print("My dog is " + str(my_dog.age) + " years old.") # 注意将数字转化为字符串！ 
  26. my_dog.sit()
  28. print("\nYour dog's name is " + your_dog.name.title() + ".")
  29. print("Your dog is " + str(your_dog.age) + " years old.")
  30. your_dog.sit()

:::tips output：
My dog’s name is Willie.
My dog is 6 years old.
Willie is now sitting.

Your dog’s name is Lucy.
Your dog is 3 years old.
Lucy is now sitting. :::

2. 给属性指定、修改默认值：

  1. """A class that can be used to represent a car."""
  3. class Car():
  4.     """A simple attempt to represent a car."""
  6.     def __init__(self, manufacturer, model, year):
  7.         """Initialize attributes to describe a car."""
  8.         self.manufacturer = manufacturer
  9.         self.model = model
  10.         self.year = year
  11.         self.odometer_reading = 0
  12.         # 👆类中的每个属性都必须有初始值。在方法_init__()内指定初始值后就无需包含为
  13.         # （接上句）它提供初始值的形参。
  15.     def get_descriptive_name(self):
  16.         """Return a neatly formatted descriptive name."""
  17.         long_name = str(self.year) + ' ' + self.manufacturer + ' ' + self.model
  18.         return long_name.title()
  20.     def read_odometer(self):
  21.         """Print a statement showing the car's mileage."""
  22.         print("This car has " + str(self.odometer_reading) + " miles on it.")
  24.     def update_odometer(self, mileage):
  25.         """
  26.         Set the odometer reading to the given value.
  27.         Reject the change if it attempts to roll the odometer back.
  28.         """
  29.         if mileage >= self.odometer_reading:
  30.             self.odometer_reading = mileage
  31.         else:
  32.             print("You can't roll back an odometer!")
  34.     def increment_odometer(self, miles):
  35.         """Add the given amount to the odometer reading."""
  36.         self.odometer_reading += miles
  1. my_used_car = Car('五菱宏光','至尊顶配','1999')
  2. print(my_used_car.get_descriptive_name())
  4. my_used_car.update_odometer(23500)
  5. my_used_car.read_odometer()
  7. my_used_car.increment_odometer(100)
  8. my_used_car.read_odometer()

:::tips output：
1999 五菱宏光 至尊顶配
This car has 23500 miles on it.
This car has 23600 miles on it. :::

二、继承

1. 关于子类

  1. """A set of classes that can be used to represent electric cars."""
  2. # 引用Car类
  3. from car import Car
  5. class Battery():
  6.     """A simple attempt to model a battery for an electric car."""
  8.     def __init__(self, battery_size=60):
  9.         """Initialize the batteery's attributes."""
  10.         self.battery_size = battery_size
  12.     def describe_battery(self):
  13.         """Print a statement describing the battery size."""
  14.         print("This car has a " + str(self.battery_size) + "-kWh battery.")  
  16.     def get_range(self):
  17.         """Print a statement about the range this battery provides."""
  18.         if self.battery_size == 60:
  19.             range = 140
  20.         elif self.battery_size == 85:
  21.             range = 185
  23.         message = "This car can go approximately " + str(range)
  24.         message += " miles on a full charge."
  25.         print(message)
  27. #Car类的子类
  28. class ElectricCar(Car):
  29.     """Models aspects of a car, specific to electric vehicles."""
  31.     def __init__(self, manufacturer, model, year):
  32.         """
  33.         初始化父类的属性👆，在初始化电动汽车特有的属性👇
  34.         """
  35.         super().__init__(manufacturer, model, year)
  36.         self.battery = Battery() #batter变量使用Battery类
  37.     # 如果想重写父类的方法，def一个同名方法即可。

2. 导入类：

1.from (文件名) import (类名)
2.import (文件名) 导入整个模块(这样做不怕重名，因为要用句点法访问)
3.from （文件名） import *导入模块中的所有类（不推荐使用，有可能会重名）

3. Python标准库：

这里只做简单介绍，如collections模块中的OrderedDict类，它相当于一个有序的字典。

  1. from collections import OrderedDict
  3. favorite_languages = OrderedDict()
  5. favorite_languages['jen'] = 'python'
  6. favorite_languages['sarah'] = 'c'
  7. favorite_languages['edward'] = 'ruby'
  8. favorite_languages['phil'] = 'python'
  10. for name, language in favorite_languages.items():
  11.     print(name.title() + "'s favorite language is " +
  12.         language.title() + ".")

:::tips output：
Jen’s favorite language is Python.
Sarah’s favorite language is C.
Edward’s favorite language is Ruby.
Phil’s favorite language is Python.
（是有序的） :::

4. 类编码风格（驼峰命名法）：

  • 类名中的每个单词首字母都大写，而不使用下划线；
  • 实例名和模块名都采用小写格式，并在每个单词之间采用下划线；
  • 每个类、模块定义后面紧跟一个文档字符串注释；