While executing the class definition which object is referenced by the first argument of the class method, Y r Object attributes not allowed as default arguments

[Krishna]

On Mar 6, 5:04 pm, "Gabriel Genellina" <gagsl-... at yahoo.com.ar> wrote:
> En Thu, 06 Mar 2008 22:48:42 -0200, Krishna <Krishna.0... at gmail.com>
> escribi�:
>
>
>
> >>>> class Test(object):
> > ...     def __init__(self):
> > ...             self.a= 2
> > ...     def func(self, k = self.a):
> > ...             print k
> > ...
> > Traceback (most recent call last):
> >   File "<stdin>", line 1, in ?
> >   File "<stdin>", line 4, in Test
> > NameError: name 'self' is not defined
>
> > In the 'definition of the class', what would the first argument 'self'
> > in the methods evaluate to; when we have an object defined, it is
> > bound to the object reference, but what happens while the class
> > definition is executed, which I believe happens when the module
> > containing the class definition is imported
>
> Function default arguments are evaluated when the function is defined
> (when the class is defined, in this case) so "self" itself has not a
> value. Try this instead:
>
>      def func(self, k=None):
>          if k is None:
>              k = self.a
>          print k
>
> If None is an allowed argument, use a special marker instead:
>
> _marker=object()
> ...
>
>      def func(self, k=_marker):
>          if k is _marker:
>              k = self.a
>          ...
>
> --
> Gabriel Genellina

Thanks for the reply. I am currently using the approach suggested by
you. But, I am more interested in knowing about the first argument
('self'), what does it hold to allow the evaluation of the method,
take the example you gave, 'self.a' as Rvalue inside the method, how
and why is this allowed, when the same 'self.a' is not allowed as the
default argument, considering the fact that I have already specified
'self' as first argument, only after whose evaluation, I believe would
the next statement (k = self.a, in def func(self, k = self.a) ) gets
evaluated

Thanks,
Krishna