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
   []
   '''