python __call__ 函數

 

 __call__

Python中有一個有趣的文法，只要定義類型的時候，實現__call__函數，這個類型就成為可調用的。

換句話說，我們可以把這個類型的對象當作函數來使用，相當於 重載了括弧運算子。

class g_dpm(object):

def __init__(self, g):

self.g = g

def __call__(self, t):

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

計算地球情境的時候，我們就可以令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
       
   []
       
   '''