Re: Re[2]: Re: class proposal

Lenard Lindstrom <[email protected]>:

> The tp_base and tp_bases slot may be defined for PyTypeObject but
> does the interpreter actually use then directly, let alone know
> about them? Or is it there as a convenience for the PyType_Type slot
> functions?  Could I define a PyTypeObject instance that does not
> actually use these slots?  I admit I am not clear on how new-style
> class types inherit through tp_base and tp_bases.

Only single inheritance exists at the C level, and it's implemented by
copying down function pointers from the type object pointed to by
tp_base (this happens when you initialise the type by calling
PyType_Ready).

As far as I know, tp_bases is only used when doing a Python attribute
lookup, and that's done by the default function installed in the
tp_getattr slot of the type object.

It would be possible to create a type object with a different
tp_getattr that implemented prototype behaviour instead of
class/instance behaviour, or a different system for Python-level
inheritance that didn't use tp_bases at all, or anything else you
wanted.

Greg Ewing, Computer Science Dept, +--------------------------------------+
University of Canterbury,	   | A citizen of NewZealandCorp, a	  |
Christchurch, New Zealand	   | wholly-owned subsidiary of USA Inc.  |
[email protected]	   +--------------------------------------+