7-2 如何爲創建大量實例節省內存定義類的__slots__屬性，它是用來聲明實例屬性名,sys.getsizeof字的列表

7-2 如何爲創建大量實例節省內存

解決方案:
定義類的slots屬性，它是用來聲明實例屬性名字的列表
有了slots之後對象就不可以再新添加屬性 p1.x

dict

import sys

class Player(object):
    def __init__(self,uid,name,status=0,level=1):
        self.uid = uid
        self.name = name
        self.status = status
        self.level = level

class Player2(object):
    __slots__= ['uid','name','status','level']
    def __init__(self,uid,name,status=0,level=1):
        self.uid = uid
        self.name = name
        self.status = status
        self.level = level

p1=Player('20014540','weihuap')
p2=Player2('20014541','weihuap')
print dir(p1)
print dir(p2)
print "the delta was %s"%(set(dir(p1))-set(dir(p2)))

print p1.__dict__
print sys.getsizeof(p1.__dict__)
print sys.getsizeof(p1)
print sys.getsizeof(p2)