I'm pretty sure I'd actually read the first 2 links you point to, but the
difference between __setattr__ and __setitem__ still never registered with
me -- perhaps partly because even the discussion of __setattr__ discusses
adding an entry to the "*dictionary* of instance attributes".
*MANY* thanks for your help!
On Thu, Aug 18, 2011 at 10:07 PM, Eric Snow <ericsnowcurren...@gmail.com>wrote:
> On Thu, Aug 18, 2011 at 7:44 PM, luvspython <srehtva...@gmail.com> wrote:
> > I'm using Python 2.7 and the code below fails at the 'super' statement
> > in the __setitem__ function in the HistoryKeeper class. The error is:
> > 'super' object has no attribute '_setitem__'
> >
> > Can anyone please tell me why and how to fix it? (I've googled
> > endlessly and I don't see the problem.)
> >
> > [The code will seem silly as it is, because it's pared down to show
> > the example. The goal is that multiple classes, like the Vehicle
> > class below, will inherit HistoryKeeper. History keeper overloads
> > __setitem__ and will eventually keep a running history every time an
> > attribute of any of the inheriting classes is changed.]
> >
> > Thanks in advance ....
> >
> >
> > class HistoryKeeper(object):
> > def __init__(self, args):
> > for arg, value in args.items():
> > if arg != 'self':
> > self.__setitem__(arg, value)
> >
> > def __setitem__(self, item, value):
> > super(HistoryKeeper, self).__setitem__(item, value)
> >
> >
> > class Vehicle(HistoryKeeper):
> > def __init__(self, tag, make, model):
> > args = locals()
> > super(Vehicle, self).__init__(args)
> >
> >
> > if __name__ == "__main__":
> > car = Vehicle('TAG123', 'FORD', 'Model A')
> > print car.make
>
> Did you mean to use __setattr__ instead? object, the base class of
> HistoryKeeper, does not have a __setitem__ method, hence the
> AttributeError. super() is a proxy for the next class in the MRO,
> typically the base class of your class.
>
> Keep in mind that <obj.tag = "TAG123"> is equivalent to
> <obj.__setattr__("tag", "TAG123")>. However, <obj["tag"] = "TAG123">
> is equivalent to <obj.__setitem__("tag", "TAG123")>.
>
> see:
>
> http://docs.python.org/reference/datamodel.html#object.__setattr__
> http://docs.python.org/reference/datamodel.html#object.__setitem__
> http://docs.python.org/library/functions.html#super
>
> -eric
>
> > --
> > http://mail.python.org/mailman/listinfo/python-list
> >
>
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