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Python编程：class类面向对象
Python编程：面向对象深入
文章内容
面向对象 类， 对象 属性和方法 封装 数据隐藏 继承(object) 代码复用 多态 接口重用 magic method魔术方法 构造对象 运算符 类的展现 类的属性访问
面向对象 类， 对象
构造函数 def __init__ 析构函数 def __del__ 新式类(object)和老式类
属性访问控制 靠自觉
public name protected _age private __weight
函数和方法(类)
public protected private method @classmethod @property
类继承
调用父类方法 super(superclass, self).method(args) superClass.method(args) isinstance issubclass 多继承
多态：继承 方法重写
magic method魔术方法
对象实例化：创建对象 -》初始化对象 __new__(cls) __init__(self) 回收对象 __del__(self) 运算符 __cmp__(self, other) __eq__(self, other) __lt__(self, other) __gt__(self, other) __add__(self, other) __sub__(self, other) __mul__(self, other) __div__(self, other) __or__(self, other) __and__(self, other) 转为字符串 __str__ -> 适合人看 __repr__ -> 适合机器看 -> eval()直接运行 __unicode__ __dir__ 设置对象属性 def __setattr__(self, name, value) self.__dict__[name] =value 错误设置，默认递归1000次 def __setattr__(self, name, value): setattr(self, name, value) 查询对象属性 __getattr__(self, name) 没有被查询到调用 __getattribute__(self, name) 每次查询都会调用 删除对象属性 __delattr__(self, name)
代码示例
类的继承
# -*- coding: utf-8 -*- # 父类 class Person(object): count = 0 # 新建对象 def __new__(cls, *args, **kwargs): print("call __new__") return super(Person, cls).__new__(cls, *args, **kwargs) # 初始化 def __init__(self, name, age, weight): print("call __init__") self.name = name self._age = age self.__weight = weight Person.count += 1 @classmethod def get_count(cls): return cls.count @property def weight(self): return self.__weight def say_hello(self): print("hello") # 子类 class EarthPerson(Person): def __init__(self, name, age, weight, language): super(EarthPerson, self).__init__(name, age, weight) self.language = language # 重写父类方法 def say_hello(self): print("hello, my name is %s"%self.name) def introduce(person): if isinstance(person, Person): person.say_hello() if __name__ == '__main__': p1 = Person("tom", 23, 60) """ call __new__ call __init__ """ p2 = EarthPerson("jack", 24, 65, "English") """ call __new__ call __init__ """ print(p1) # <__main__.Person object at 0x106fb2350> print(p1.__dict__) # {'_age': 23, 'name': 'tom', '_Person__weight': 60} print(dir(p1)) """ ['_Person__weight', '__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', '_age', 'count', 'get_count', 'name', 'say_hello', 'weight'] """ print(p1.name) # tom print(p1._age) # 23 print(p1._Person__weight) # 60 print(p1.weight) # 60 print(Person.count) # 2 print(Person.get_count()) # 2 p1.say_hello() # hello print(p2) # <__main__.EarthPerson object at 0x106fb2390> print(issubclass(EarthPerson, Person)) # True print(isinstance(p2, Person)) # True p2.say_hello() # hello, my name is jack introduce(p2) # hello, my name is jack introduce(p1) # hello
魔术方法
class Point(object): def __init__(self, x, y): self.x = x self.y = y def __eq__(self, other): if isinstance(other, Point): if self.x == other.x and self.y == other.y: return True else: return False else: raise Exception("the type must be Ponit") def __add__(self, other): if isinstance(other, Point): x = self.x + other.x y = self.y + other.y return Point(x, y) else: raise Exception("the type must be Ponit") def __str__(self): return "Ponit(x={x}, y={y})".format(x=self.x, y=self.y) def __dir__(self): return self.__dict__.keys() def __getattribute__(self, name): # return getattr(self, name) 错误 # return self.__dict__[name] 错误 return super(Point, self).__getattribute__(name) def __setattr__(self, name, value): # setattr(self, name, value) 错误 self.__dict__[name] = value if __name__ == '__main__': point1 = Point(1, 2) point2 = Point(1, 2) print(point1 == point2) # True print(point1 + point2) # Ponit(x=2, y=4) print(dir(point1)) # ['x', 'y']
