A few examples of __dict__. Thanks Eric!

dict_examples.py

# Let's create a dummy class
>>> class ABC(object):
...     pass
... 

# Let's see if it works for the class
>>> ABC.__dict__
<dictproxy object at 0x2b83b7887750>
>>> dict(ABC.__dict__)
{'__dict__': <attribute '__dict__' of 'ABC' objects>, '__module__': '__main__', '__weakref__': <attribute '__weakref__' of 'ABC' objects>, '__doc__': None}
>>> ABC.x = 1
>>> dict(ABC.__dict__)
{'__dict__': <attribute '__dict__' of 'ABC' objects>, 'x': 1, '__module__': '__main__', '__weakref__': <attribute '__weakref__' of 'ABC' objects>, '__doc__': None}

# Let's see if it works for the instances
>>> inst = ABC()
>>> inst.__dict__
{}
>>> inst.y = 2
>>> inst.__dict__
{'y': 2}

# However, it doesn't exist for builtins like string
>>> s = "astring"
>>> s.__dict__
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'str' object has no attribute '__dict__'