rights.
4¡¢the fourth is a smart reference that ¡°performs additional actions
when an object is accessed¡±.We can use the same coding approach for all proxies,
although the fourth use case¡¯s behavior could also be achieved using a descriptor
"""
# sample 1
# a virtual proxy that allows us to create lightweight objects instead of
# heavyweight objects, only creating the heavyweight objects if they are actually
# needed
from PIL import Image as Image
YELLOW, CYAN, BLUE, RED, BLACK = (Image.color_for_name(color)
for color in ("yellow", "cyan", "blue", "red", "black"))
class ImageProxy:
def __init__(self, ImageClass, width=None, height=None, filename=None):
assert (width is not None and height is not None) or filename is not None
self.Image = ImageClass
self.commands = []
if filename is not None:
self.load(filename)
else:
self.commands = [(self.Image, width, height)]
def load(self, filename):
self.commands = [(self.Image, None, None, filename)]
