[Python-Dev] __getstate__() not inherited when __slots__ present

[Greg Ward]

If a class and its superclass both define __slots__, it appears that
__getstate__() is not inherited from the superclass.  Example:

"""
class Base (object):
    __slots__ = []

    def __getstate__ (self):
        return tuple([getattr(self, attr) for attr in self.__slots__])

class Thing (Base):
    __slots__ = ['a', 'b']

    def __init__ (self):
        self.a = 42
        self.b = "boo!"

abstract = Base()
thing = Thing()

print abstract.__getstate__
print thing.__getstate__
"""

When I run this with a not-quite-current CVS Python:

  <bound method Base.__getstate__ of <__main__.Base object at 0x401f73b8>>
  <built-in function __getstate__>

The upshot of this is that I can't just define one __getstate__() in the
superclass of a bunch of __slots__-using classes -- I guess I'll have to
set __getstate__ manually for each class.  ;-(  If this is a feature, is
it documented anywhere?

(BTW, I see the same behaviour with Python 2.2.2.)

        Greg
-- 
Greg Ward <gward@python.net>                         http://www.gerg.ca/
"Very funny, Scotty.  Now beam my *clothes* down."