python __call__ 函数

__call__

Python中有一个有趣的语法，只要定义类型的时候，实现__call__函数，这个类型就成为可调用的。

换句话说，我们可以把这个类型的对象当作函数来使用，相当于 重载了括号运算符。

class g_dpm(object):

def __init__(self, g):

self.g = g

def __call__(self, t):

return (self.g*t**2)/2

计算地球场景的时候，我们就可以令e_dpm = g_dpm(9.8)，s = e_dpm(t)。

 

1.       
         
         
         
   
          
          
          
          
    
           
    
            class Animal 
            ( 
            object 
            ): 
           
          
          
          
          
    
           
    
            def 
            __init__ 
            ( 
            self, name, legs 
            ): 
           
          
          
          
          
    
           
    
            self. 
            name = name 
           
          
          
          
          
    
           
    
            self. 
            legs = legs 
           
          
          
          
          
    
           
    
            self. 
            stomach = 
            [ 
            ] 
           
          
          
          
          
    
           
   
               
           
          
          
          
          
    
           
    
            def 
            __call__ 
            ( 
            self,food 
            ): 
           
          
          
          
          
    
           
    
            self. 
            stomach. 
            append 
            (food 
            ) 
           
          
          
          
          
    
           
   
               
           
          
          
          
          
    
           
    
            def poop 
            ( 
            self 
            ): 
           
          
          
          
          
    
           
    
            if 
            len 
            ( 
            self. 
            stomach 
            ) > 
            0: 
           
          
          
          
          
    
           
    
            return 
            self. 
            stomach. 
            pop 
            ( 
            0 
            ) 
           
          
          
          
          
    
           
   
               
           
          
          
          
          
    
           
    
            def 
            __str__ 
            ( 
            self 
            ): 
           
          
          
          
          
    
           
    
            return 
            'A animal named %s' % 
            ( 
            self. 
            name 
            ) 
           
          
          
          
          
    
           
   
               
           
          
          
          
          
    
           
   
             cow = Animal 
            ( 
            'king', 
            4 
            ) 
            #We make a cow 
           
          
          
          
          
    
           
   
             dog = Animal 
            ( 
            'flopp', 
            4 
            ) 
            #We can make many animals 
           
          
          
          
          
    
           
    
            print 
            'We have 2 animales a cow name %s and dog named %s,both have %s legs' % 
            (cow. 
            name, dog. 
            name, cow. 
            legs 
            ) 
           
          
          
          
          
    
           
    
            print cow 
            #here __str__ metod work 
           
          
          
          
          
    
           
   
               
           
          
          
          
          
    
           
    
            #We give food to cow 
           
          
          
          
          
    
           
   
             cow 
            ( 
            'gras' 
            ) 
           
          
          
          
          
    
           
    
            print cow. 
            stomach 
           
          
          
          
          
    
           
   
               
           
          
          
          
          
    
           
    
            #We give food to dog 
           
          
          
          
          
    
           
   
             dog 
            ( 
            'bone' 
            ) 
           
          
          
          
          
    
           
   
             dog 
            ( 
            'beef' 
            ) 
           
          
          
          
          
    
           
    
            print dog. 
            stomach 
           
          
          
          
          
    
           
   
               
           
          
          
          
          
    
           
    
            #What comes inn most come out 
           
          
          
          
          
    
           
    
            print cow. 
            poop 
            ( 
            ) 
           
          
          
          
          
    
           
    
            print cow. 
            stomach 
            #Empty stomach 
           
          
          
          
          
    
           
   
               
           
          
          
          
          
    
           
    
            '' 
            '-->output 
           
          
          
          
          
    
           
    
            We have 2 animales a cow name king and dog named flopp,both have 4 legs 
           
          
          
          
          
    
           
    
            A animal named king 
           
          
          
          
          
    
           
    
            ['gras 
            '] 
           
          
          
          
          
    
           
    
            ['bone 
            ', 'beef 
            '] 
           
          
          
          
          
    
           
    
            gras 
           
          
          
          
          
    
           
    
            [] 
           
          
          
          
          
    
           
    
            ' 
            ''