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how to pass globals across modules (wxPython)

Peter Hansen peter at engcorp.com
Mon Dec 20 05:01:05 EST 2004 
Martin Drautzburg wrote:
> My wxPython program starts execution in mainFrame.py like this
>         def main():
>                 global application
>                 application=MainApp(0)
>                 application.MainLoop()
> 
> I need to access the "application" object from other modules, actually
> the windows and frames that live therein and I don't know how to do
> this.
> 
> I tried using "global", but that does not seem to help. In the other
> module I run an "import mainFrame" and that seems to reset the global
> variables.
> 
> Am I missing something obvious?

Not exactly obvious, perhaps, but well-defined.  When you run
a Python script, the first script executed (the one specified
on the command line) is given the name __main__ in the list
of loaded modules (sys.modules, specifically).  If you do an
"import mainFrame", you are actually loading a second copy
of the module into memory, under a different name.

The solution to your specific problem, without changing any
of the structure of your program, is to do "import __main__"
instead, but that's ultimately not likely the best solution.

One slightly better solution would be to create a special
empty module, just for holding "application globals" like
this, say "globals.py".  Then you can import that in your
main script, and do "globals.application = MainApp(0)",
then import the same name elsewhere and work with it as you
are trying to.

An even better approach might be to find a way to avoid
having to access the main window through a global, but
I'll have to leave this up to you, as it may depend on
your program structure.

-Peter
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