optional argument to a subclass of a class

[Alex Hall]

On 5/20/10, Patrick Maupin <pmaupin at gmail.com> wrote:
> On May 20, 9:56 pm, Alex Hall <mehg... at gmail.com> wrote:
>> Hi all,
>> I am now trying to allow my classes, all of which subclass a single
>> class (if that is the term), to provide optional arguments. Here is
>> some of my code:
>>
>> class Craft():
>>  def __init__(self,
>>  name,
>>  isAircraft=False,
>>  id=helpers.id(),
>>  hits=0,
>>  weapons=[]):
>>   self.name=name
>>   self.id=id
>>   self.hits=hits
>>   self.weapons=weapons
>>   self.isAircraft=isAircraft
>>  #end def
>> #end class
>>
>> #now a class for each type of craft in the game
>> #each will subclass the Craft class, but each also has its own settings
>>
>> class Battleship(Craft):
>>  def __init__(self,
>>  name,
>>  maxHits):
>>   Craft.__init__(self, name)
>>   self.maxHits=maxHits
>>   self.length=maxHits #in Battleship, each ship's length is the same
>> as how many times it can be hit
>>  #end def
>> #end class
>>
>> I want to be able to say something like
>> b=Battleship("battleship1", 4, weapons=["missile1","missile2"])
>> When I do that, though, I get a traceback on the above line saying
>> "type error: __init__() got an unexpected keyword argument 'weapons'".
>> What did I do wrong / what do I need to change so that any Craft
>> (Battleship, Carrier, and so on) can optionally provide a list of
>> weapons, or any other arguments to which I assign default values in my
>> Craft class? I hope this makes sense.
>>
>> --
>> Have a great day,
>> Alex (msg sent from GMail website)
>> mehg... at gmail.com;http://www.facebook.com/mehgcap
>
> You overrode the __init__method from the superclass.
I know, I thought I had to in order to make all of Craft's attribs
available to the Battleship. Is that not the case?
>
> One thing you can do is in battleship, you can accept additional
> keyword arguments:
>
>     def __init__(self, name, ..., **kw):
>
> Then you could invoke the superclass's init:
>
>     Craft.__init__(self, name, **kw)
So how do I get at anything inside **kw? Is it a list?
>
> Regards,
> Pat
> --
> http://mail.python.org/mailman/listinfo/python-list
>


-- 
Have a great day,
Alex (msg sent from GMail website)
mehgcap at gmail.com; http://www.facebook.com/mehgcap