Jan Eden a écrit :
> Hi,
>
> Jan Eden wrote on 26.08.2005:
>
>
>>Hi,
>>
>>I need to use an instance attribute as the default value for a parameter to a
>>method.
>>
>>This obviously won't work:
>>
>>page.Children()
>>
>>def Children(self, id=self.id, level=2):
>>
>>How can I get the id parameter to use the attribute page.id? I know I could
>>simply use the method call
>>
>>page.Children(id=page.id)
>>
>>but I thought it is much more elegant to use a default value here.
>>
>>Is it possible?
>
>
> Addition: I do use
>
> def Children(self, id=0, level=2):
> if not id: id = self.id
>
> right now. But still - there has to be a smarter way.
Well, I prefer the use of "None" for that, as it cannot be mixed up with
any other value:
def Children(self, id=None, level=2):
if id is None: id = self.id
Another possibility (mainly if you have many such arguments) is the use
of something like:
def Children(self, **kwords):
id = kwords.pop("id", None)
level = kwords.pop("level", 2)
Although it is not equivalent ! In the second cases, you have to name
the parameter to set it ! But I sometimes find this A Good Thing (tm)
when no argument order is better ...
Pierre
--
Pierre Barbier de Reuille
INRA - UMR Cirad/Inra/Cnrs/Univ.MontpellierII AMAP
Botanique et Bio-informatique de l'Architecture des Plantes
TA40/PSII, Boulevard de la Lironde
34398 MONTPELLIER CEDEX 5, France
tel : (33) 4 67 61 65 77 fax : (33) 4 67 61 56 68
_______________________________________________
Tutor maillist - Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor
