Question

I have a Python class with many methods with signature:

def select_xxx(self, arg1 , arg2 , .. argn, intersect = False)

I.e. the methods have a varying (1-3) number of positional arguments, and an optional argument intersect with default value False. I would like to decorate all of these methods with a decorater which will insepect the value of the intersect parameter and take different actions accordingly. My current approach is something like this:

def select_decorator(select_method):

  def select_wrapper( self , *args, intersect = False , **kwargs)
     if intersect:
        # Special init code for intersect == True
        select_method( self , *args , **kwargs)
     else:
        # Normal call path for intersect == False 
        select_method( self , *args , **kwargs)

  return select_wrapper  

@select_decorator
select_xxx( self , arg1 , arg2 , intersect = False)

But getting the optional argument intersect into the *args and **kwargs mix inside the decorator is currently no joy. I could sacrifice the **kwargs functionality if that makes the problem easier to solve. Any suggestions?

Joakim

Answer 1

I am assuming that intersect will always be passed as keyword argument. In which case you could simply do this inside you decorator

def select_decorator(select_method):

  def select_wrapper( self , *args, **kwargs):
     intersect = kwargs.has_key('intersect') and kwargs['intersect']
     if intersect:
        # Special init code for intersect == True
        select_method( self , *args , **kwargs)
     else:
        # Normal call path for intersect == False 
        select_method( self , *args , **kwargs)
  return select_wrapper