The reason for this is that the c source code wich is executed when the
build in function Hash is executed on a python object wich has as C type
PyObject then following code is executed (in the latest python 2.6).
PyObject_Hash(PyObject *v)
{
PyTypeObject *tp = v->ob_type;
if (tp->tp_hash != NULL)
return (*tp->tp_hash)(v);
/* more code wich in this case doesn't get executed hence isn't relevant
}
So as you can see, as soon as the class of v does have a tp_hash
attribute/method wich is not NULL it will always call that without looking
at the attributes of the instance.
The reason why you get a different behaviour for old style classes is
because they have a different c type.
To get arround it we would have to hack the python c source code.
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