[Python-Dev] RFC: readproperty

[Barry Warsaw]

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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