Python subclass does not have dict while the superclass has?

Question

In the below example, the superclass has a __dict__ attribute, while the subclass does not have it.

>>> class Super(object):
...     def hello(self):
...        self.data1="hello"
... 
>>> 
>>> class Sub(Super):
...     def hola(self):
...        self.data2="hola"
... 
>>> 
>>> Super.__dict__
<dictproxy object at 0x108794868>
>>> Super.__dict__.keys()
['__dict__', '__module__', '__weakref__', 'hello', '__doc__'] # note __dict__
>>> Sub.__dict__.keys()
['__module__', '__doc__', 'hola']   #__dict__ absent here
>>> Sub.__dict__
<dictproxy object at 0x108794868>

Q1: The comments on the above shows where dict is present. why the superclass has it but not the sublcass.

while trying to find out the answer for this, I came across this post. and this confused me further.

>>> class Foo(object):
...    __slots__ = ('bar',)
...    bar="spam"
... 
>>> f = Foo()
>>> f.__dict__
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'Foo' object has no attribute '__dict__'
>>> class A(object):
...    pass
... 
>>> b = A()
>>> b.__dict__
{}

Q2: why the instance of Foo throws AttributeError but that of A has empty dict.

Here's [some info](http://stackoverflow.com/questions/4877290/what-is-the-dict-dict-attribute-of-a-python-class) about `__dict__['__dict__']`, but it doesn't make clear why it's not in the subclass. — hunse, Nov 18 '13 at 20:24

score 0 · Answer 1 · answered May 25 '14 at 17:44

0

Class with slots hasn't dict. Here there is conflict between 'bar' and slots. Delete 'bar' and it will work fine.

answered May 25 '14 at 17:44

Ilya Afanasyev

61
2

Python subclass does not have __dict__ while the superclass has?

1 Answers1

Python subclass does not have dict while the superclass has?