instance introspection and __slots__

David Mertz, Ph.D. mertz at gnosis.cx
Wed Oct 16 06:32:29 CEST 2002


|def attr_dict(o, fillslots=0):
|    if hasattr(o,'__dict__'): [...]
|    elif hasattr(o,'__slots__'): [...]
|    else:
|        raise TypeError, "Object has neither __dict__ nor  __slots__"

"Delaney, Timothy" <tdelaney at avaya.com> wrote previously:
|You may want to add the case where an object has both __dict__ and
|__slots__.

I'm probably just being daft here... but would you show me an object
that has both __dict__ and __slots__?  I kinda thought the one excluded
the other (but I'm probably not accounting for some inheritence case or
something).  E.g.

    >>> class Slotty(object):
    ...     __slots__ = ('foo','bar')
    ...     def __init__(self):
    ...         self.foo = 1
    ...         self.bar = 2
    ...
    >>> slotty = Slotty()
    >>> slotty.__slots__
    ('foo', 'bar')
    >>> slotty.__dict__
    Traceback (most recent call last):
      File "<stdin>", line 1, in ?
    AttributeError: 'Slotty' object has no attribute '__dict__'
    >>> slotty.other = 3
    Traceback (most recent call last):
      File "<stdin>", line 1, in ?
    AttributeError: 'Slotty' object has no attribute 'other'
    >>> class NoSlot(object):
    ...     def __init__(self):
    ...         self.foo = 1
    ...         self.bar = 2
    ...
    >>> noslot = NoSlot()
    >>> noslot.__slots__
    Traceback (most recent call last):
      File "<stdin>", line 1, in ?
    AttributeError: 'NoSlot' object has no attribute '__slots__'
    >>> noslot.__dict__
    {'foo': 1, 'bar': 2}
    >>> noslot.other = 3
    >>> noslot.__dict__
    {'foo': 1, 'bar': 2, 'other': 3}

Yours, David...




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