[Python-3000] [Python-Dev] PEP 367: New Super (original) (raw)

Tim Delaney timothy.c.delaney at gmail.com
Thu May 31 15:25:17 CEST 2007

Guido van Rossum wrote:

The patch notes say that you're actually inserting a keyword-only argument - is this purely meant to be a stopgap measure so that you've got a local (which could be put into a cell)? I'm not using a cell because I'm storing the result of calling super(Class, self) -- that is different for each instance, while a cell would be shared by all invocations of the same function.

I'm actually investigating another (possibly complementary) option at the moment - adding an im_super attribute to methods, which would store either a bound or unbound super instance when the bound or unbound method object is created. method_new becomes:

static PyObject * method_new(PyTypeObject* type, PyObject* args, PyObject *kw) { PyObject *func; PyObject *self; PyObject *classObj = NULL;

if (!_PyArg_NoKeywords("instancemethod", kw))
    return NULL;
if (!PyArg_UnpackTuple(args, "method", 2, 3,
              &func, &self, &classObj))
    return NULL;
if (!PyCallable_Check(func)) {
    PyErr_SetString(PyExc_TypeError,
            "first argument must be callable");
    return NULL;
}
if (self == Py_None)
    self = NULL;
if (self == NULL && classObj == NULL) {
    PyErr_SetString(PyExc_TypeError,
        "unbound methods must have non-NULL im_class");
    return NULL;
}

return PyMethod_New(func, self, classObj);

}

then in method_call we could have:

static PyObject * method_call(PyObject *func, PyObject *arg, PyObject *kw) { PyObject *self = PyMethod_GET_SELF(func); PyObject *klass = PyMethod_GET_CLASS(func); PyObject *supervalue = PyMethod_GET_SUPER(func);

and populate the super argument from supervalue. I think im_super has uses on its own (esp. for introspection).

Presumably with this approach you could call the method like:

A().func(1, 2, super=object()) No, because that would be a syntax error (super as a keyword is only allowed as an atom). You could get the same effect with A().func(1, 2, **{'super': object()}) but that's so obscure I don't mind.

I'd prefer to eliminate it, but that's a detail that can be taken care of later.

Anyway, need to go to bed - have to be up in 6 hours.

Cheers,

Tim Delaney

More information about the Python-3000 mailing list