@staticmethod 靜態方法

函數修飾符，用來修飾一個函數，類似於裝飾器

class Dog(object):
    def __init__(self,name):
        self.name = name

    def eat(self,food):
        print(‘%s is eating %s‘%(self.name,food))

d = Dog(‘二哈‘)
d.eat(‘包子‘)      #二哈 is eating 包子

eat()方法上面加上 @staticmethod

class Dog(object):
    def __init__(self,name):
        self.name = name
    @staticmethod
    def eat(self,food):
        print(‘%s is eating %s‘%(self.name,food))

d = Dog(‘二哈‘)
d.eat(‘包子‘)  #TypeError: eat() missing 1 required positional argument: ‘food‘

提示 food 少傳遞一個參數

刪除food參數嘗試下

class Dog(object):
    def __init__(self,name):
        self.name = name
    @staticmethod
    def eat(self):
        print(‘%s is eating %s‘%(self.name,‘包子‘))

d = Dog(‘二哈‘)
d.eat()  #TypeError: eat() missing 1 required positional argument: ‘self‘

提示少一個位置參數self ，self默認不是自動傳進去的嗎，靜態方法就是截斷方法與類的聯系，就是說eat在這裏就只是一個單純的函數。

調用方式：類名。靜態方法（） 也可以用對象調用方法的方式。

class Dog(object):
    def __init__(self,name):
        self.name = name
    @staticmethod
    def eat():
        print(‘%s is eating %s‘%(‘5545‘,‘包子‘))

d = Dog(‘二哈‘)
d.eat()    #5545 is eating 包子
Dog.eat() #5545 is eating 包子

要在靜態方法裏面調用self，就必須把self本身傳進去

class Dog(object):
    def __init__(self,name):
        self.name = name
    @staticmethod
    def eat(self):
        print(‘%s is eating %s‘%(self.name,‘包子‘))

d = Dog(‘二哈‘)
d.eat(d)       #二哈 is eating 包子

靜態方法名義上歸類管理，實際上調用不了類或者實例的任何屬性。

@classmethod 類方法

函數修飾符，同樣用來裝飾函數

class Dog(object):
    def __init__(self,name):
        self.name = name
    @classmethod
    def eat(self):
        print(‘%s is eating %s‘%(self.name,‘包子‘))

d = Dog(‘二哈‘)
d.eat() #AttributeError: type object ‘Dog‘ has no attribute ‘name‘

嘗試訪問類變量

class Dog(object):
    name= ‘秋田‘
    def __init__(self,name):
        self.name = name
    @classmethod
    def eat(self):
        print(‘%s is eating %s‘%(self.name,‘包子‘))

d = Dog(‘二哈‘)
d.eat() #秋田 is eating 包子

類方法只能訪問類變量，不能訪問實例變量。

property 屬性方法

class Dog(object):
    name= ‘秋田‘
    def __init__(self,name):
        self.name = name
    @property
    def eat(self):
        print(‘%s is eating %s‘%(self.name,‘包子‘))

d = Dog(‘二哈‘)
d.eat() #TypeError: ‘NoneType‘ object is not callable

去掉括號

class Dog(object):
    name= ‘秋田‘
    def __init__(self,name):
        self.name = name
    @property
    def eat(self):
        print(‘%s is eating %s‘%(self.name,‘包子‘))

d = Dog(‘二哈‘)
d.eat  #二哈 is eating 包子

把一個方法變成靜態屬性

作為一個屬性，如果有參數要怎麽傳遞？

既然是屬性就是可以賦值的。

class Dog(object):
    name= ‘秋田‘
    def __init__(self,name):
        self.name = name
    @property
    def eat(self,food):
        print(‘%s is eating %s‘%(self.name,food))

d = Dog(‘二哈‘)
d.eat = ‘包子‘ #AttributeError: can‘t set attribute

直接賦值也是不可以的，同樣需要裝飾下

class Dog(object):
    name= ‘秋田‘
    def __init__(self,name):
        self.name = name
        self._food = None
    @property
    def eat(self):
        print(‘%s is eating %s‘%(self.name,self._food))
    @eat.setter
    def eat(self,food):
        print(‘set food is‘,food)
        self._food = food

d = Dog(‘二哈‘)
d.eat = ‘包子‘ #set food is 包子
d.eat           #二哈 is eating 包子

屬性賦值會觸發 @eat.setter 下的 eat()方法。

刪除屬性

class Dog(object):
    name= ‘秋田‘
    def __init__(self,name):
        self.name = name
        self.__food = None
    @property
    def eat(self):
        print(‘%s is eating %s‘%(self.name,self._food))
    @eat.setter
    def eat(self,food):
        print(‘set food is‘,food)
        self.__food = food
 
d = Dog(‘二哈‘)
d.eat = ‘包子‘
d.eat
del d.eat #AttributeError: ‘Dog‘ object has no attribute ‘_food‘

默認是不能刪除的，如果非要刪除就要重寫

class Dog(object):
    name= ‘秋田‘
    def __init__(self,name):
        self.name = name
        self.__food = None
    @property
    def eat(self):
        print(‘%s is eating %s‘%(self.name,self.__food))
    @eat.setter
    def eat(self,food):
        print(‘set food is‘,food)
        self.__food = food

    @eat.deleter
    def eat(self):
        del self.__food
        print(‘刪除成功‘)

d = Dog(‘二哈‘)
d.eat = ‘包子‘ set food is 包子
d.eat  # 二哈 is eating 包子
del d.eat  # 刪除成功
d.eat   # AttributeError: ‘Dog‘ object has no attribute ‘_Dog__food‘

d.eat調用了@property下的eat 因為這個方法裏面有調用self.__food 而這個屬性被刪除了

有些場景不能簡單的通過定義靜態屬性來實現的。所有要把方法做成屬性。比如有些接口的API。

staticmethod classmethod property方法