On Dec 8, 2007 9:45 AM, Marcin 'Qrczak' Kowalczyk <[EMAIL PROTECTED]> wrote: > I'm confused about storing methods in class dictionaries from the point > of view of the C API. > > 1. Let's say that I have a callable PyObject called f, of my type > defined in C. I want to store something derived from f as A.m > for some class A, such that for an object a of class A, calling > a.m(*args) ends up calling f(a, *args). > > In Python2 PyMethod_New(f, NULL, a) seems to be the right to store > in the class. How to do the equivalent thing in Python3?
Add a __get__ (instance) method to f's class, and store f directly in A. Your __get__ method should return a bound object using PyMethod_New(f, a). > BTW, applying PyMethod_Type to 3 arguments crashes Python3. I think > this line is the culprit (classobject.c): > > if (!PyArg_UnpackTuple(args, "method", 2, 3, > &func, &self)) > > Should be 2 instead of 3. There used to be an extra parameter. Thanks for noting! Christian Heimes fixed this already. > 2. As above, but f is to be implemented as a C function. I found the > following working for a new-style class: > > - make PyMethodDef struct for the method > - use PyDescr_NewMethod > - store the resulting object in the class > > but it does not work for a classic class (such that an exception > class in Python 2.4 and below) to which I want to add a method. > Here it seems to be doable differently: > > - make PyMethodDef struct for the method, but with an unused first > parameter > - use PyCFunction_New, with NULL as 'self' > - use PyMethod_New on the resulting function, NULL, and the class > - store the resulting object in the class > > Can this be done simpler? Having separate variants for different > Python versions is OK. Unsure how this differs from the previous case. I'd recommend wrapping f in another class defined in C. -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-3000 mailing list Python-3000@python.org http://mail.python.org/mailman/listinfo/python-3000 Unsubscribe: http://mail.python.org/mailman/options/python-3000/archive%40mail-archive.com
