Re: [Jython-users] exec and globals

[Frank C. <fc...@pu...>]

Thanks for the great reply. Lots of useful information here. I would
appreciate seeing your example code too.

Do I have it right that Jython can't catch Java exceptions? If so, should I
implement my Java code to catch and store all exceptions and have a geterror
method that returns a thrown error code to the Jython script?

-Frank


-- 
Frank Cohen, founder, PushToTest, www.pushtotest.com, phone: 408 374 7426
Come to PushToTest for Load, a free open-source tool for performance and
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> From: Ype Kingma <yk...@xs...>
> Date: Sat, 22 Sep 2001 11:09:01 +0100
> To: jyt...@li...
> Subject: Re: [Jython-users] exec and globals
> 
> Frank,
> 
>> If anyone will confirm this is the best way to use exec and globals, I would
>> certain appreciate your feedback.
>> 
>> The goal is to have the Jython equivalent of server-side include files where
>> one script calls another and can share variables. In an experiment I created
>> two files:
>> 
>> exec_example.py
>> 
>> def makethecall:
>> i=100
>> exec open("included.py").read()
>> print "j=", j
>> makethecall()
>> 
>> 
>> included.py
>> 
>> j=101
>> print "i=", i
>> 
>> By running exec_example I see:
>> 
>> i=100
>> j=101
>> 
>> Is this the best way to have scripts calling other scripts and returning
>> results?
> 
> This illustrates that the global namespace passed to exec is the local
> namespace of the makethecall function.
> You can have more control over the namespaces passed to exec by passing
> these as arguments, too. My guess is that you are going to need this.
> In this particular example I think I'd prefer to use execfile(), but
> that is rather minor.
> 
> You could also note that:
> - the __name__ variable in the executed code will have the value of the
> __name__ variable at the exec call, which might not be desirable.
> - the function makethecall is defined when included.py is exec'ed,
> 
> There are a few other things that are normally provided by jython
> itself for the code it executes that you might want to consider:
> 
> In case you want to control import's in exec'ed code:
> - sys.modules might change during the exec when the executed code imports
> other modules.
> - neither exec nor execfile does any module administration in
> sys.modules. You can do this yourself by (temporarily) adding
> a new.module() to sys.modules.
> In case you want more control over imports in executed code you'll need to
> control sys.path too, as it determines the places from which modules can
> be loaded.
> 
> The exec'ed code might throw
> - a jython exception. You might want to catch it.
> - a java exception that you cannot catch in jython.
> 
> The exec'ed code might not return. This is rather hard to control,
> but it is possible in jython by using a (deprecated) java call to stop
> the thread doing the exec. Fortunately the python language does not
> encourage writing endless loops.
> 
> The nice thing about python/jython is that you can control almost all
> of these aspects when using exec or execfile.
> The downside is off course that you might have to write the code to do
> some of this. If you'd like to see an example, let me know.
> 
> Regards,
> Ype
> 
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