[Neil Schemenauer, on the gc.garbage docs as of about a week ago]
It's not clear because it's nonsense. I think I mean to say something about the gc.garbage binding. If you do something like:
gc.garbage = "ha ha"
then the list is garbage is forever inaccessible from within Python.
I've since tried to repair the docs, to point out that rebinding gc.garbage is a Bad Idea but mutating it may be a Good one. BTW, I expect it's more likely people will get in trouble via: gc.garbage = [] I expect that because I did it once <wink>.
Is there some way to prevent people from assigning to certain module variables?
Not that I know of. If you're terribly concerned, gc could look up "garbage" in its dict on each access. That's what, e.g., PRINT_ITEM does with sys.stdout. Then it would also have to check that it's a list, etc. But I'd be keener to see new words spelling out which parts of the gc interface are and aren't intended "to work" across releases ...