custom plugin architecture: how to see parent namespace?

[faulkner]

On Jul 22, 10:06 am, escalation746 <escalation... at yahoo.com> wrote:
> I've got a namespace query that amounts to this: How can an imported
> function see data in the parent custom namespace? I have read through
> numerous posts which skirt this issue without answering it.
>
> To illustrate, create plugin.py with a couple of functions. The second
> will obviously fail.
>
> ----
> def Hello():
>         print 'hello'
>
> def ViewValuable():
>         print VALUABLE
> ----
>
> Then create master.py which loads the plugin at runtime, later running
> various code fragments against it.
>
> ----
> # location of plugin module
> filespec = '/path/to/plugins/plugin.py'
> filepath, filename = os.path.split(filespec)
> filename = os.path.splitext(filename)[0]
>
> # add to system path
> if filepath not in sys.path:
>         sys.path.append(filepath)
>
> # import into our namespace
> space = __import__(filename, globals(), locals(), [])
> namespace = space.__dict__
>
> # sometime later in the code... define a new function
> def _plus():
>         print 'plus'
>
> # add that to our namespace
> namespace.update({'Plus': _plus, 'VALUABLE': 'gold'})
>
> # run custom code
> code = """
> Hello()
> Plus()
> Valuable()
> """
> exec code in namespace
> ----
>
> This code will echo the lines:
> hello
> plus
>
> Followed by a traceback for:
> NameError: global name 'VALUABLE' is not defined
>
> The question is: How do I get a function in plugin.py to see VALUABLE?
> Using external storage of some sort is not viable since many different
> instances of plugin.py, all with different values of VALUABLE, might
> be running at once. (In fact VALUABLE is to be a key into a whole
> whack of data stored in a separate module space.)
>
> Extensive modifications to plugin.py is also not a viable approach,
> since that module will be created by users. Rather, I need to be able
> to pass something at execution time to make this happen. Or create an
> access function along the lines of _plus() that I can inject into the
> namespace.
>
> Any help, please? I've been losing sleep over this one.
>
> -- robin

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