[Python-Dev] Weakref design questions

[Brian Quinlan]

Martin wrote:

> So you merely want a proxy, not a weak proxy: both for the 
> entire object, and for the methods. So for this code, you 
> can save the proxy, and return your callable object. Make 
> the null pointer check in its tp_call slot, and don't kill 
> it after py func call, but merely clear the pointer.

As you say, I need a proxy for my methods and a proxy for my objects. 

Creating my own proxy type for methods is easy, since the only
interesting thing that must be proxied is __call__.

Creating my own proxy type for arbitrary objects is harder because I
must create a proxy for every slot that I use. That requires duplication
a lot of the work that already lives in weakrefobject.c

Also, for both method and object proxies, I have to invent a mechanism
to signal that the original object is dead. weakrefobject.c already
defines a nice mechanism.

> I also notice that you rely on the fact that Python code has no way 
> to find out the underlying object of a weak proxy. I think this is a
weak
> assumption - there is no guarantee that this is not possible, or might
> not be possible in the future.

This is a concern. If I am mistaken in my assumption, please let me know
and I will either invent my own proxy type or use the
check-on-every-method-call technique.

Cheers,
Brian