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

Steven Majewski sdm7g@Virginia.EDU
Mon, 17 Dec 2001 18:43:48 -0500 (EST)

On Mon, 17 Dec 2001, Guido van Rossum wrote:

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.

But even if that is possible, another problem with implementing it in a Python extension module is that Python objects are not (except for maybe functions and things that drag along a reference to global module namespace) "owned" by their modules in anything like the association between Lisp symbols and their packages: python modules can import other modules or can dynamically add things to their namespaces. We can't just iterate through a module dict and 'zero' out all of the objects there.

So that's not a useful idea, alas.

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!

-- Steve