slots.py

Python 2.7.14 (default, Sep 23 2017, 22:06:14) 
[GCC 7.2.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.

>>> class Wat(object):
...     __slots__ = ('a', 'b')
...     a = 42
... 

>>> x = Wat()

>>> x.a
42

>>> x.b
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: b


>>> Wat.a
42

>>> Wat.b
<member 'b' of 'Wat' objects>

>>> type(Wat.b)
<type 'member_descriptor'>