[Python-3000] C API changes? [Was: Python 3000 Process]

[Neil Schemenauer]

On Tue, Mar 21, 2006 at 05:01:31PM +0100, Thomas Wouters wrote:
> I would like Pythonic code to be usable in both 2.x (where x is,
> say, 6 or higher) and 3.0, but 3.0 shouldn't need to worry too
> much about it.

The other question I haven't seen much discussion about is C API
changes.  Are we hoping that people can port extension modules with
little effort or are we going to be doing lots of cleanup?

Some possible areas of cleanup:

    * Use unions for PyObject structure (allowing strict aliasing
      by the compiler).

    * Move GC attributes into the PyObject structure (e.g. similar
      to how ob_size works).

    * Rethink weakref implementation (not sure about details but
      maybe we can do better).

    * Rationalize method structures (e.g. sq_concat and sq_repeat
      could go away since we can use nb_add and nb_multiply).

    * Rationalize finalizer behavior (e.g. get rid of __del__
      methods in favor of guardians?).

    * Make it easier to write simple extension types.  For example,
      there could be standard tp_clear and tp_traverse methods that
      could work if the object is simply an array of PyObject pointers.

    * Do we still need tp_print and tp_repr?

    * Register instead of stack based VM?


One part of me hopes that we could do a lot of cleanup in these
areas.  Another part is concerned about badly breaking the huge
number of extensions out there (a major reason for Python's success,
IMO).  In any case, I hope an important objective of P3K will be to
make writing extensions even easier.

  Neil