[Pyobjc-dev] Re: [Python-Dev] Bridging strings from Python to other languages

[Bill Bumgarner]

On Wednesday, Feb 5, 2003, at 10:52 US/Eastern, Guido van Rossum wrote:
> In my experience almost no Python code depends on this property, and
> it seems to be the most problematic one.  So why is this a
> requirement?

Because we are using Python to glue together other object oriented 
frameworks-- Apple's and third party's-- for which we do not have 
control over said behavior.

Sometimes an object is just an object and those frameworks insist on 
the same object-- same identifier/address-- coming out that went in.

As Just pointed out, my original example wasn't as clear as it could 
have been.   If a String object comes out of the alien-to-python world 
and is later sent from python back into the alien-to-python runtime, 
the same String object-- the same id()-- must be sent back.

> If you can live with only using Unicode strings (even when all they
> contain is ASCII or Latin-1 values), I think subclassing Unicode might
> be the way to go.

Right.  I believe that is the path will we go down.

> I don't have time to dig deeper into this.  But if you think a small
> change to Python can make life easier for you, I expect we'll be happy
> to implement it, as long as it doesn't make life harder for Python
> developers.

I can think of a couple of changes to Python that would be potentially 
quite helpful in this situation.

Specifically:

     - ability to have weak references to string objects [and unicode 
objects].   Since we can make arbitrary object associations and 
re-associations when crossing the bridge between environments, I 
believe weakref would allow us to maintain a reference map as long as 
we could grab the 'string is now going away' callback to update the 
weakref map when the string is deallocated

     - ability to subclass string objects or the ability to add a hunk 
of data-- the reference to the 'alien' string object-- to any string 
object.

Either one would work equally as well... whether or not they are easy 
to do, I have not a clue.

b.bum