instance introspection and __slots__

[David Mertz, Ph.D.]

"Rod Mancisidor" <mancisidor at computer.org> wrote previously:
|I used to be able to find all the direct attributes of an instance by using
|__dict__.  With python 2.2 this is no longer possible since __dict__ may not
|even exist and when it does it will not include the attributes in the union
|of all the __slots__ in the MRO of the instance.

In my gnosis.util.introspect module which is included in
<http://gnosis.cx/download/Gnosis_Utils-current.tar.gz>, I use the
following implementation:

    class undef: pass
    def attr_dict(o, fillslots=0):
        if hasattr(o,'__dict__'):
            return o.__dict__
        elif hasattr(o,'__slots__'):
            dct = {}
            for attr in o.__slots__:
                if fillslots and not hasattr(o, attr):
                    setattr(o, attr, undef())
                    dct[attr] = getattr(o,attr)
                elif hasattr(o, attr):
                    dct[attr] = getattr(o,attr)
            return dct
        else:
            raise TypeError, "Object has neither __dict__ nor __slots__"

YMMV (and I might even change it later).

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