__slots__ are not inherited demo

class X(object):
    __slots__ = ('hi',)

class Y(X):
    __slots__ = ('bye',)
    
x = X()
print(x.__slots__)
# ('hi',)

y = Y()
print(y.__slots__)
# ('bye',)

y.bye = 'yep'  # of course this works.
y.hi = 'yep' # this works too even though 'hi' is not in y.__slots__
y.seeya = 'ERROR HERE!!' # slots are working.

class Z(X):
   pass  # no slots

z = Z()
print(z.__slots__)
# ('hi',)
z.blah = 5 # works great

# z has slots and a dict.
print(z.__dict__)
{'blah': 5}

# in defining __getstate__ on X, if you want X to be inherited properly, 
# it needs to search in the .__class__.mro() for all __slots__, and
# also check to see if a __dict__ exists.

Line 12 shows that slots are actually inherited. I guess that you meant that __slots__ is not inherited.

Thanks! There was some ambiguity. Updated.