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. 1. class Animal ( object ):
   2. def __init__ ( self, name, legs ):
   3. self. name = name
   4. self. legs = legs
   5. self. stomach = [ ]
   6.  
   7. def __call__ ( self,food ):
   8. self. stomach. append (food )
   9.  
   10. def poop ( self ):
   11. if len ( self. stomach ) > 0:
   12. return self. stomach. pop ( 0 )
   13.  
   14. def __str__ ( self ):
   15. return 'A animal named %s' % ( self. name )
   16.  
   17. cow = Animal ( 'king', 4 ) #We make a cow
   18. dog = Animal ( 'flopp', 4 ) #We can make many animals
   19. print 'We have 2 animales a cow name %s and dog named %s,both have %s legs' % (cow. name, dog. name, cow. legs )
   20. print cow #here __str__ metod work
   21.  
   22. #We give food to cow
   23. cow ( 'gras' )
   24. print cow. stomach
   25.  
   26. #We give food to dog
   27. dog ( 'bone' )
   28. dog ( 'beef' )
   29. print dog. stomach
   30.  
   31. #What comes inn most come out
   32. print cow. poop ( )
   33. print cow. stomach #Empty stomach
   34.  
   35. '' '-->output
   36. We have 2 animales a cow name king and dog named flopp,both have 4 legs
   37. A animal named king
   38. ['gras ']
   39. ['bone ', 'beef ']
   40. gras
   41. []
   42. ' ''