"""http://codesnipers.com/?q=python-flyweights"""
import weakref
class Card(object):
"""The object pool. Has builtin reference counting"""
_CardPool = weakref.WeakValueDictionary()
"""Flyweight implementation. If the object exists in the
pool just return it (instead of creating a new one)"""
def __new__(cls, value, suit):
obj = Card._CardPool.get(value + suit, None)
if not obj:
obj = object.__new__(cls)
Card._CardPool[value + suit] = obj
obj.value, obj.suit = value, suit
return obj
# def __init__(self, value, suit):
# self.value, self.suit = value, suit
def __repr__(self):
return "<Card: %s%s>" % (self.value, self.suit)
if __name__ == '__main__':
# comment __new__ and uncomment __init__ to see the difference
c1 = Card('9', 'h')
c2 = Card('9', 'h')
print(c1, c2)
print(c1 == c2)
print(id(c1), id(c2))
点击run it 运行之！！！