[Python-Dev] class name spaces inside an outer function (original) (raw)

Benjamin Peterson benjamin at python.org
Sun Apr 28 05:28:36 CEST 2013

2013/4/27 Nick Coghlan <ncoghlan at gmail.com>:

On Sun, Apr 28, 2013 at 11:38 AM, Benjamin Peterson <benjamin at python.org> wrote:

2013/4/27 Nick Coghlan <ncoghlan at gmail.com>:

On 28 Apr 2013 04:30, "Ethan Furman" <ethan at stoneleaf.us> wrote:

I filed bug http://bugs.python.org/issue17853 last night. If somebody could point me in the right direction (mainly which files to look in), I'd be happy to attempt a patch. Hmm, interesting challenge. A key part of the problem is that the 3.x compiler assumes there's no way to inject names it doesn't know about into code inside a function - we missed the fact that you could still do it with a nested class and a metaclass prepare method. That's not the problem. You can't inject names dynamically into a function scope with variables in a class scope, since nothing closes over them. Yeah, what I wrote didn't quite capture what I meant: - in Python 2.x, using LOADDEREF when a nested class body references a lexically scoped name is correct - in Python 3.x, it is no longer correct, because prepare may inject additional names that the compiler doesn't know about

You could still get the same "bug" in Python 2 by messing with locals() in a class within a function.

-- Regards, Benjamin

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