[Python-Dev] Adding types.build_class for 3.3

[Nick Coghlan]

On Thu, May 10, 2012 at 6:11 PM, Mark Shannon <mark at hotpy.org> wrote:
> Finally, could you remind me how the proposed type.define differs from
> builtins.__build_class__?
> I can't see any difference (apart from parameter ordering and the extra name
> parameter in builtins.__build_class__).

It's the officially supported version of that API - the current
version is solely a CPython implementation detail. The main change is
moving exec_body to the end and making it optional, thus bringing the
interface more in line with calling a metaclass directly. The name
parameter is actually still there, I just forgot to include in the
examples in the thread.

You'll find there's no mention of __build_class__ in the language or
library references, thus there's currently no official way to
programmatically define a new type in a way that complies with PEP
3115.

(This is explained in the tracker issue and the previous thread that
proposed the name operator.build_class)

I prefer type.define(), but if the descriptor protocol does cause
problems (and making static methods callable doesn't fix them), then
we'll move it somewhere else (probably types.define() with a new
_types module).

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia