[Python-Dev] RFC: readproperty (original) (raw)

Barry Warsaw barry at python.org
Thu Sep 29 00:23:15 CEST 2005

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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