On Sun, Nov 30, 2014 at 10:14 PM, Mark Shannon <m...@hotpy.org> wrote: > Hi, > > This discussion has been going on for a while, but no one has questioned the > basic premise. Does this needs any change to the language or interpreter? > > I believe it does not. I'm modified your original metamodule.py to not use > ctypes and support reloading: > https://gist.github.com/markshannon/1868e7e6115d70ce6e76
Interesting approach! As written, your code will blow up on any python < 3.4, because when old_module gets deallocated it'll wipe the module dict clean. And I guess even on >=3.4, this might still happen if old_module somehow manages to get itself into a reference loop before getting deallocated. (Hopefully not, but what a nightmare to debug if it did.) However, both of these issues can be fixed by stashing a reference to old_module somewhere in new_module. The __class__ = ModuleType trick is super-clever but makes me irrationally uncomfortable. I know that this is documented as a valid method of fooling isinstance(), but I didn't know that until your yesterday, and the idea of objects where type(foo) is not foo.__class__ strikes me as somewhat blasphemous. Maybe this is all fine though. The pseudo-module objects generated this way will still won't pass PyModule_Check, so in theory this could produce behavioural differences. I can't name any specific places where this will break things, though. From a quick skim of the CPython source, a few observations: It means the PyModule_* API functions won't work (e.g. PyModule_GetDict); maybe these aren't used enough to matter. It looks like the __reduce__ methods on "method objects" (Objects/methodobject.c) have a special check for ->m_self being a module object, and won't pickle correctly if ->m_self ends up pointing to one of these pseudo-modules. I have no idea how one ends up with a method whose ->m_self points to a module object, though -- maybe it never actually happens. PyImport_Cleanup treats module objects differently from non-module objects during shutdown. I guess it also has the mild limitation that it doesn't work with extension modules, but eh. Mostly I'd be nervous about the two points above. -n -- Nathaniel J. Smith Postdoctoral researcher - Informatics - University of Edinburgh http://vorpus.org _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
