[Python-Dev] RFC: readproperty

[Guido van Rossum]

It doesn't work that way for new-style classes.

On 9/28/05, Barry Warsaw <barry at python.org> wrote:
> On Wed, 2005-09-28 at 10:16, Jim Fulton wrote:
>
> > When we ask for the eggs attribute the first time, we call the
> > descriptor, which calls the eggs function.  The function sets the eggs
> > attribute, overriding the descriptor. The next time the eggs attribute
> > is accessed, the saved value will be used without calling the
> > descriptor.
> >
> > I do this often enough that I think it would be useful to include it
> > in python, either as a builtin (like property) or in the library.  (Or
> > possibly by adding an option to property to generate a read
> > descriptor.) I'd be happy to add this for 2.5.
>
> I /must/ be missing something.  Why not just use property as a
> decorator?
>
> class C:
>     @property
>     def eggs(self):
>         print 'in eggs'
>         self.eggs = 7
>         return self.eggs
>
> >>> c = C()
> >>> c.eggs
> in eggs
> 7
> >>> c.eggs
> 7
>
> -Barry
>
>
>
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--Guido van Rossum (home page: http://www.python.org/~guido/)