Python面向对象静态方法,类方法,属性方法
属性:
公有属性 (属于类,每个类一份)
普通属性 (属于对象,每个对象一份)
私有属性 (属于对象,跟普通属性相似,只是不能通过对象直接访问)
方法:(按作用)
构造方法
析构函数
方法:(按类型)
普通方法
私有方法(方法前面加两个下划线)
静态方法
类方法
属性方法
静态方法
@staticmethod
静态方法,通过类直接调用,不需要创建对象,不会隐式传递self
类方法
@classmethod
类方法,方法中的self是类本身,调用方法时传的值也必须是类的公有属性,
就是说类方法只能操作类本身的公有字段
class Dog(object): food = "gutou" age = "1" def __init__(self, name): self.NAME = name @classmethod def eat(self,age): #只能是类中的变量 # print(self.NAME) print(age) print(self.food) @classmethod def eat1(self, age): # 只能是类中的变量 # print(self.NAME) age = "2" self.food = "tang" @staticmethod def print_1(): print(Dog.food, Dog.age) d = Dog("labuladuo") d.eat(Dog.age) #通过对象调用 Dog.eat(Dog.age) #通过类调用 print("-----1-----") d.eat1(Dog.age) Dog.print_1() print("--------2-------") Dog.eat1(Dog.age) Dog.print_1()
属性方法
属性变为私有属性,加断言
class Cycle(object): def __init__(self,x,y,radius): self.x = x self.y = y self.radius = radius @property def radius(self): return self.__radius @radius.setter def radius(self,radius): assert radius > 0, "radius must be nonzero and non-negative" self.__radius = radius @radius.deleter def radius(self): del self.__radius def __str__(self): return "({0},{1},{2})".format(self.x,self.y,self.radius) c = Cycle(1,1,7) c.radius = 9 print(c) del c.radius print(c.radius) #(1,1,9) #AttributeError: 'Cycle' object has no attribute '_Cycle__radius'
class Dog(object): def __init__(self, name): self.name = name self.__food = None # def eat(self, food):原始方式 # self.__food = food # print('%s eat %s' %(self.name, food)) @property def eat(self): print('%s eat %s' %(self.name,self.__food)) @eat.setter def eat(self, food): self.__food = food @eat.deleter def eat(self): del self.__food print("删完了") d = Dog("labuladuo") # d.eat("baozi") #原始方式 d.eat d.eat = "baozi" d.eat #调用方式没变,只是改变传入的参数就改变了结果 #可以删除__food属性 del d.eat d.eat # 报错 '''输出 labuladuo eat None labuladuo eat baozi 删完了 AttributeError: 'Dog' object has no attribute '_Dog__food' '''
属性方法应用场景
好吧,把一个方法变成静态属性有什么卵用呢?既然想要静态变量,那直接定义成一个静态变量不就得了么?well, 以后你会需到很多场景是不能简单通过 定义 静态属性来实现的, 比如 ,你想知道一个航班当前的状态,是到达了、延迟了、取消了、还是已经飞走了, 想知道这种状态你必须经历以下几步:
1. 连接航空公司API查询
2. 对查询结果进行解析
3. 返回结果给你的用户
因此这个status属性的值是一系列动作后才得到的结果,所以你每次调用时,其实它都要经过一系列的动作才返回你结果,但这些动作过程不需要用户关心, 用户只需要调用这个属性就可以,明白 了么?
class Flight(object): def __init__(self,name): self.flight_name = name def checking_status(self): print("checking flight %s status " % self.flight_name) return 1 @property def flight_status(self): status = self.checking_status() if status == 0 : print("flight got canceled...") elif status == 1 : print("flight is arrived...") elif status == 2: print("flight has departured already...") else: print("cannot confirm the flight status...,please check later") f = Flight("CA980") f.flight_status
cool , 那现在我只能查询航班状态, 既然这个flight_status已经是个属性了, 那我能否给它赋值呢?试试吧
f = Flight("CA980") f.flight_status f.flight_status = 2
输出, 说不能更改这个属性,我擦。。。。,怎么办怎么办。。。
checking flight CA980 status flight is arrived... Traceback (most recent call last): File "/Users/jieli/PycharmProjects/python基础/自动化day7面向对象高级/属性方法.py", line 58, in <module> f.flight_status = 2 AttributeError: can't set attribute
当然可以改, 不过需要通过@proerty.setter装饰器再装饰一下,此时 你需要写一个新方法, 对这个flight_status进行更改。
![](https://images.cnblogs.com/OutliningIndicators/ExpandedBlockStart.gif)
class Flight(object): def __init__(self,name): self.flight_name = name def checking_status(self): print("checking flight %s status " % self.flight_name) return 1 @property def flight_status(self): status = self.checking_status() if status == 0 : print("flight got canceled...") elif status == 1 : print("flight is arrived...") elif status == 2: print("flight has departured already...") else: print("cannot confirm the flight status...,please check later") @flight_status.setter #修改 def flight_status(self,status): status_dic = { 0 : "canceled", 1 :"arrived", 2 : "departured" } print("\033[31;1mHas changed the flight status to \033[0m",status_dic.get(status) ) @flight_status.deleter #删除 def flight_status(self): print("status got removed...") f = Flight("CA980") f.flight_status f.flight_status = 2 #触发@flight_status.setter del f.flight_status #触发@flight_status.deleter