At 02:04 AM 6/28/2007 +0100, tav wrote: >rehi all, > >I have been looking at the object capability + Python discussions for >a while now, and was wondering what the use cases for >``object.__subclasses__`` and ``FunctionType.func_closure`` were? > >I don't see __subclasses__ used anywhere in the standard library. And >whilst I can see exposing func_closure as being useful in terms of >"cloning/modifying" an existing function, isn't it possible to do that >without making it introspectable?
You know, I find it particularly interesting that, as far as I can tell, nobody who proposes making changes to the Python language to add security, ever seems to offer any comparison or contrast of their approaches to Zope's -- which doesn't require any changes to the language. :) >Now, whilst probably wrong, I can see myself being able to create a >minimal object capability system in pure python if those 2 "features" >disappeared. Am I missing something obvious that prevents me from >doing that? Well, you're missing a simpler approach to protecting functions, anyway. The '__call__' attribute of functions is still callable, but doesn't provide any access to func_closure, func_code, etc. I believe this trick also works for bound method objects. I suspect that you could also use ctypes to remove or alter the type.__subclasses__ member, though I suppose you might not consider that to be "pure" Python any more. However, if you use a definition of pure that allows for stdlib modules, then perhaps it works. :) >Can we get rid of them for Python 2.6? Or even 2.5.2? Is anyone >besides PJE actually using them? ;p I wouldn't object (no pun intended) to moving the type.__subclasses__ method to say, the 'new' or 'gc' modules, since you wouldn't want to make those available to restricted code, but then they'd still be available for folks who need/want them. 'gc' has similar capabilities (again no pun intended) anyway. However, ISTM that this should be a 3.0 change rather than a 2.x one, even so. With regard to the func_closure thing, I'd actually like to make it *writable* as well as readable, and I don't mean just to change the contents of the cells. But, since you can use .__call__ to make a capability without access to func_closure, it doesn't seem like you really need to remove func_closure. _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
