python的__dict__属性详解

1.无处不在的__dict__
首先看下类的__dict__属性和类对象的__dict__属性，

class A(object):
    """
    Class A.
    """

    a = 0
    b = 1

    def __init__(self):
        self.a = 2
        self.b = 3

    def test(self):
        print( 'a normal func.')

    @staticmethod
    def static_test(self):
        print ('a static func.')

    @classmethod
    def class_test(self):
        print ('a calss func.')


obj = A()
print (A.__dict__)
print (obj.__dict__)

运行结果如下：
{‘module’: ‘main’, ‘doc’: '\n Class A.\n ', ‘a’: 0, ‘b’: 1, ‘init’: init at 0x00000167D3C809D8>, ‘test’: , ‘static_test’: , ‘class_test’: , ‘dict’: dict’ of ‘A’ objects>, ‘weakref’: weakref’ of ‘A’ objects>}
{‘a’: 2, ‘b’: 3}

由此可见，类的静态函数，类函数，普通函数，全局变量以及内置属性都放在类__dict__中，对象的__dict__中存储了self.xx的东西。

2.Python中常用的数据类型没有__dict__属性。

num = 3
ll = []
dd = {}
print num.__dict__
print ll.__dict__
print dd.__dict__

运行结果会报错。