what's the biggest difference between dir and __dict__ in python

Question

class C(object):
    def f(self):
        print self.__dict__
        print dir(self)
c = C()
c.f()

output:

{}

[\'__class__\', \'_         


        

Answer 1

The function f belongs to the dictionary of class C. c.__dict__ yields attributes specific to the instance c.

>>> class C(object):
    def f(self):
        print self.__dict__


>>> c = C()
>>> c.__dict__
{}
>>> c.a = 1
>>> c.__dict__
{'a': 1}

C.__dict__ would yield attributes of class C, including function f.

>>> C.__dict__
dict_proxy({'__dict__': , '__module__': '__main__', '__weakref__': , '__doc__': None, 'f': })

While an object can refer to an attribute of its class (and indeed all the ancestor classes), the class attribute so referred does not become part of the associated dict itself. Thus while it is legitimate access to function f defined in class C as c.f(), it does not appear as an attribute of c in c.__dict__.

>>> c.a = 1
>>> c.__dict__
{'a': 1}