python的__slots__

看python社区大妈组织的内容里边有一篇讲python内存优化的，用到了__slots__。然后查了一下，总结一下。感觉非常有用

python类在进行实例化的时候，会有一个__dict__属性，里边有可用的实例属性名和值。声明__slots__后，实例就只会含有__slots__里有的属性名。

# coding: utf-8class A(object):    x = 1    def __init__(self):        self.y = 2a = A()print a.__dict__print(a.x, a.y)a.x = 10a.y = 10print(a.x, a.y)class B(object):    __slots__ = ('x', 'y')    x = 1    z = 2    def __init__(self):        self.y = 3        # self.m = 5  # 这个是不成功的b = B()# print(b.__dict__)print(b.x, b.z, b.y)# b.x = 10# b.z = 10b.y = 10print(b.y)class C(object):    __slots__ = ('x', 'z')    x = 1    def __setattr__(self, name, val):        if name in C.__slots__:            object.__setattr__(self, name, val)    def __getattr__(self, name):        return "Value of %s" % namec = C()print(c.__dict__)print(c.x)print(c.y)# c.x = 10c.z = 10c.y = 10print(c.z, c.y)c.z = 100print(c.z)

{'y': 2}(1, 2)(10, 10)(1, 2, 3)10Value of __dict__1Value of y(10, 'Value of y')100