[Python-Dev] Should we do away with unbound methods in Py3k? (original) (raw)

Christian Heimes lists at cheimes.de
Sat Nov 24 08:10:31 CET 2007

Guido van Rossum wrote:

Index: Objects/funcobject.c =================================================================== --- Objects/funcobject.c (revision 59154) +++ Objects/funcobject.c (working copy) @@ -643,8 +643,10 @@ static PyObject * funcdescrget(PyObject *func, PyObject *obj, PyObject *type) { - if (obj == PyNone) - obj = NULL; + if (obj == PyNone || obj == NULL) { + PyINCREF(func); + return func; + } return PyMethodNew(func, obj, type); } [well, except those should be tabs not spaces]

I've created a preliminary patch. Several unit tests are still failing.

The patch is also changing some semantics. For example in Python 2.5:

import inspect class Class(object): ... def method(self): pass ... inspect.ismethod(Class().method) True inspect.ismethod(Class.method) True

But in py3k:

import inspect class Class: ... def method(self): pass ... inspect.ismethod(Class().method) True inspect.ismethod(Class.method) False # !!!

Without support from the descriptor it's not possible to distinguish a function from an unbound method any more. I like to add im_class to the function object. I don't see negative side effects, do you?

/* Bind a function to an object */ static PyObject * func_descr_get(PyObject *func, PyObject *obj, PyObject *type) { if (obj == Py_None || obj == NULL) { Py_INCREF(func); if (type) { PyObject_SetAttrString(func, "im_class", type); } else { PyObject_SetAttrString(func, "im_class", Py_None); } return func; } return PyMethod_New(func, obj, type); }

http://bugs.python.org/issue1493

Christian

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