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
             
            
   
             
   
              []
             
            
   
             
   
              '
              ''