__slots__创建大量类的实例节省内存

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


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

p1 = Player('001', 'Jim')
p2 = Player2('001', 'Jim')


# 单个对象差不了多少,如果是面对万级别的对象,才有点用
import sys
print(sys.getsizeof(p1),'--01') # 56 --01
print(sys.getsizeof(p2),'--02')  # 72 --02


print(dir(p1))
print(dir(p2))
print(set(dir(p1)) - set(dir(p2)))   # {'__weakref__', '__dict__'}
print(p1.__dict__)    # {'uid': '001', 'name': 'Jim', 'stat': 0, 'level': 1}
p1.x = 2
print(p1.__dict__)  # {'uid': '001', 'name': 'Jim', 'stat': 0, 'level': 1, 'x': 2}
p1.__dict__['y'] = 3
print(p1.__dict__)  # {'uid': '001', 'name': 'Jim', 'stat': 0, 'level': 1, 'x': 2, 'y': 3}



p2.x = 2
print(p2.x)  # AttributeError: 'Player2' object has no attribute 'x'
# print(p2.__dict__)  # AttributeError: 'Player2' object has no attribute '__dict__'