Re: [Jython-users] Interpreters within Interpreters

[Edward P. <epo...@te...>]

Hi Ype,

> It is a bit tricky to share namespaces this way. An alternative is to
> use the namespace of a module shared between the main app and the
interpreters.
> You can set things in a module from outside the module.
I am not sure I see the difference. This is what I am doing:
MainApp:
sharedSpace={'this':this, 'that':that, 'whatever':whatever}
globals().update(sharedSpace)

Then I have 'plugins':
plugin.init(sharedSpace)

In the plugin:
def init(namespace):
    globals().update(namespace)

Now each plugin may create additional interpreters, and the main app
normally has at least one interpreter.

So far, I think this has the same effect as a module. But I see what you
mean:
import sharedSpace:
thatRef = sharedSpace.that
etc.

> Unpleasant things might happen when you explicitly clear a namespace too
early.
> Only removing references is safer.
I am sorry, my python newbieness is showing. Explicity clear a namespace?
If in my plugin I:
del that
then I remove it from the modules namespace. It is still alive elsewhere (I
assume) as the GC won't clean up until I del that from all the namespaces
that contain its reference. Right?

> You could use the thread id as the distinguishing criterion. Ie. replace
> sys.stderr with an object that uses the thread id to send it's output
> to different places. See demos/swing/Console.py on changing sys.stdout
> and sys.stderr.
I considered the thread ID, but not all interpreters are in different
threads.
Perhaps I could 'register' a module/threadID pair as a key, and then look
back at the call stack to see which module using stdout/err. And if no key
exists, then the original stdout is used. Heh, heh, I am not sure I can do
this, just assuming I can peek back into the call stack.

> You might consider using the namespace of a new.module()
is the new module available in Jython? 'import new' doesn't work here.


> Some modules use their __name__ to find their module in sys.modules
> (notably PyUnit) and supporting this is nice.
> When each interpreter thread finishes you can remove all the references
> from sys.modules to make sure nothing is dangling.
Thanks, didn't know about this, will have to look in the docs.

> I have some bad experience with clearing such namespaces, so i'd recommend
> to only remove the references. The garbage collector will find non
> referenced objects in due time.
Again, I am a little confused ... clearing vs removing references. I am
guessing, in an interpreters __del__
I set my variables to None? And leave stuff in sys.modules alone?

> Finally: when you use exec of execfile() you don't need a PyInterpreter.
> To set things in a module name space before it is started
> just use module.__dict__['var'] = value.
At the moment I am just adding a console to my app, so I can interactively
do things - an intermediate step befiore commiting to a user interface.

Thanks for all your tips, seems there is little one can't change in Python
... still trying to get used to this coming from c++/java :)

-Ed