[Tutor] Class Attribute "Overloading?"

[Vincent Gulinao]

I see, I think "property" is what I'm looking for.

But how would you design it yourself (you said it's a little ugly, I love to
hear better ideas)? My only concern is to avoid unnecessary DB accesses (or
any other expensive processes).

Thanks.

On 8/16/07, Tiger12506 <keridee at jayco.net> wrote:
>
>
> > Sorry about that. I want something like:
> >
> > class foo:
> >
> >    def __init__(self):
> >
> >         self.attr1 = None
> >
> >
> >    def get_attr1(self):
> >
> >         if not self.attr1:
> >
> >             attr1 = <get value from DB, very expensive query>
> >
> >             self.attr1 = attr1
> >
> >         return self.attr1
> >
> >
> > such that:
> >
> > foo_instance = foo()
> >
> > then:
> >
> > foo_instance.get_attr1()
> >
> > and
> >
> > foo_instance.attr1
> >
> > gets the same value.
> >
> > Such that you get to derive attr1 only as needed and just once, both
> > outside
> > and within foo class.
> >
> > Or is it a bad idea or just plain ugly to do something like that? If it
> > is,
> > kindly suggest better approach.
> >
> > Thanks.
>
> It's a little ugly but not too bad. What you are describing are
> properties.
>
> class Foo:
>   def _get_attr1(self):
>      if not self.attr1:
>         attr1 = TheValue
>      return attr1
>   def _set_attr1(self, value):
>      self.attr1 = value
>      ChangeDBFunction(value)
>   attr1 = property(self._get_attr1,self._setattr1,None,None)
>
> I think that will work. The docs seem to suggest that you should subclass
> `object`.
> JS
>
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>
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