[Python-Dev] regrtest.py mystery (original) (raw)

Guido van Rossum guido@python.org
Mon, 17 Dec 2001 19:15:59 -0500

> Python doesn't let you replace a reference to an object with something > else -- except in special cases (e.g. with explicit weak refs) there's > no way to know where references to an object might exist.

I was too fuzzy in my choice of words. What I meant was not finding and replacing the references, but replacing the object to which all of the 'dangling references' point. But that won't work either: Python objects share the same head, but total size of the object structs are too variable, and I don't know it's possible to make the minimal size object show the required behaviour.

In general it's impossible. You can't even replace the type pointer with a pointer to a dummy type, because it would leak any objects referenced from the original object, and it would break if the original object lived in a special free list.

If the problem was important enough, I think a way could be found around those problems above, but I'm still not sure that module unloading isn't a solution looking for a problem!

Well, there are a bunch of people who want to undo a partial import, and that boils down to about the same thing.

--Guido van Rossum (home page: http://www.python.org/~guido/)