Help Understanding weakref (lazyloader)

[Ripter]

I found this script at http://www.pygame.org/wiki/LazyImage...arent=CookBook
And I can't quite figure out how it works. I was wondering if someone
could clarify it for me.
The Code is:

import pygame
import weakref

class ResourceControl ler(object):
def __init__(self, loader):
self.__dict__.u pdate(dict(
names = {},
cache = weakref.WeakVal ueDictionary(),
loader = loader
))

def __setattr__(sel f, name, value):
self.names[name] = value

def __getattr__(sel f, name):
try:
img = self.cache[name]
except KeyError:
img = self.loader(sel f.names[name])
self.cache[name] = img
return img


class ImageController (ResourceContro ller):
def __init__(self):
ResourceControl ler.__init__(se lf, pygame.image.lo ad)


My question is why does the __setattr__ set the value to
self.names[name] instead of self.cache[name]?

[Ripter]

Re: Help Understanding weakref (lazyloader)

On Sep 3, 10:46 pm, Ripter <Ripter...@gmai l.comwrote:

I found this script athttp://www.pygame.org/wiki/LazyImageLoadin g?parent=CookBo ok
And I can't quite figure out how it works. I was wondering if someone
could clarify it for me.
The Code is:
>
import pygame
import weakref
>
class ResourceControl ler(object):
    def __init__(self, loader):
        self.__dict__.u pdate(dict(
            names = {},
            cache = weakref.WeakVal ueDictionary(),
            loader = loader
        ))
>
    def __setattr__(sel f, name, value):
        self.names[name] = value
>
    def __getattr__(sel f, name):
        try:
            img = self.cache[name]
        except KeyError:
            img = self.loader(sel f.names[name])
            self.cache[name] = img
        return img
>
class ImageController (ResourceContro ller):
    def __init__(self):
        ResourceControl ler.__init__(se lf, pygame.image.lo ad)
>
My question is why does the __setattr__ set the value to
self.names[name] instead of self.cache[name]?

I feel stupid, I figured it out. (Don't program while watching Back to
the Future)
The reason would be the 'lazy' part. self.names holds the file name,
and when you get the property back (__getattr__) it checks to see if
it already got the value or not, and uses the name to get the value if
it hasn't already.

Duh. Sorry.