calling superclass' method with list positional arg

[Roeland Rengelink]

Steven Haryanto wrote:
> 
> My Bag's constructor accepts a list positional args to fill
> the object with initial data, so I can conveniently create
> a bag initially filled with stuff like this:
> 
> mybag = Bag("apples", "oranges", "money")
> 
> BagOTricks is a subclass of Bag, and it needs to do something
> else but let the superclass do the actual data filling.
> Currently I do it like this:
> 
> class Bag:
> 
>      def __init__(self, *items):
>          self._items = list(items)
> 
>      def add(self, item):
>          self._items.append(item)
> 
> class BagOTricks(Bag):
> 
>      def __init__(*args):
>          self = args_[0]
>          # do something else first...
> 
>          # then pass the items to superclass' constructor
>          apply(Bag.__init__, args_)
> 
> Is there an elegant way to do this so I can still declare
> Bag's __init__ as 'def __init__(self, *items)', but I don't
> need to create a temporary list like below?
> 
> class BagOTricks(Bag):
> 
>      def __init__(self, *items):
>          # do something else first...
> 
>          # then pass the items to superclass' constructor

>          args = list(items)
>          args.insert(0, self)

Shouldn't that args be a tuple: i.e: args = (self,)+items ?

>          apply(Bag.__init__, args)
> 
> Thanks,
> Steve

I may misunderstand the question, but maybe this is what you mean
(Python 2.0+)

class BagOTricks(Bag):
    def __init__(self, *items):
       # do something else
       Bag.__init__(self, *items)

If you're using 1.5.* and want to avoid the copies, the __init__(*args)
method
seems like the best approach On the other hand. why worry about the
copies, the
__init__ is not going to take that many arguments is it?

Or just not call Bag.__init__. but do the assignment in BagOTricks
itself.

Hope this helps,

Roeland