Jython concurrency in the PythonInterpreter class

[Ted Larson Freeman]

I am investigating the use of Jython to replace a simple home-grown
scripting language for a Java application. I'm instantiating a
PythonInterpreter and executing an entire jython file at once, like
this:

PythonInterpreter interp = new PythonInterpreter();
interp.execfile("test.py");

It works beautifully for sequential execution of Java method calls,
but I'm uncertain as to the best way to implement concurrent
execution. In my first attempt, using threads, "test.py" included code
like this:

from threading import Thread
Thread(JavaClassA.methodA()).start()
Thread(JavaClassB.methodB()).start()

This is a simple case with no shared data between methodA and methodB.
Both methods write to a log4j log file. The entries in the log file
appear sequentially, labeled as running on thread "MainThread". That
is, the results are the same as if I just do this:

JavaClassA.methodA()
JavaClassB.methodB()

Is the PythonInterpreter class capable of creating new threads? Is
there a better technique for concurrency that I should use instead?

Any comments are greatly appreciated.

Thanks.

Ted

------------------------------------------------------------------------------
Enter the BlackBerry Developer Challenge  
This is your chance to win up to $100,000 in prizes! For a limited time,
vendors submitting new applications to BlackBerry App World(TM) will have
the opportunity to enter the BlackBerry Developer Challenge. See full prize  
details at: http://p.sf.net/sfu/Challenge
_______________________________________________
Jython-users mailing list
Jython-users@...
https://lists.sourceforge.net/lists/listinfo/jython-users

[Charlie Groves]

Hi Ted,

On Wed, Jul 8, 2009 at 1:32 PM, Ted Larson
Freeman<freeman@...> wrote:
> In my first attempt, using threads, "test.py" included code
> like this:
>
> from threading import Thread
> Thread(JavaClassA.methodA()).start()
> Thread(JavaClassB.methodB()).start()

Check out the docs for the Thread object:
http://docs.python.org/library/threading.html#thread-objects  The
first argument is the thread group, so you're setting the thread group
for your threads with the results of methodA and methodB.  Since
you're calling methodA and methodB to create arguments for Thread,
they're run in the main thread.

What you want to do is set the target of the Thread to the function or
method you want invoked on the new thread, and then call start.  For
example, the code below calls add on an ArrayList on a separate
thread:

Jython 2.5.0+ (trunk:6503:6505M, Jul 8 2009, 18:36:14)
[Java HotSpot(TM) 64-Bit Server VM (Apple Inc.)] on java1.6.0_13
Type "help", "copyright", "credits" or "license" for more information.
>>> from threading import Thread
>>> from java.util import ArrayList
>>> l = ArrayList()
>>> Thread(target=l.add, args=(5,)).start()
>>> l
[5]

The args keyword arg is a tuple of positional arguments to pass to the
target method.

With your examples, you'd want to do
Thread(target=JavaClassA.methodA).start() and
Thread(target=JavaClassB.methodB).start().

Hope this helps,
Charlie

------------------------------------------------------------------------------
Enter the BlackBerry Developer Challenge  
This is your chance to win up to $100,000 in prizes! For a limited time,
vendors submitting new applications to BlackBerry App World(TM) will have
the opportunity to enter the BlackBerry Developer Challenge. See full prize  
details at: http://p.sf.net/sfu/Challenge
_______________________________________________
Jython-users mailing list
Jython-users@...
https://lists.sourceforge.net/lists/listinfo/jython-users

[Ted Larson Freeman]

Thanks for the clear and amazingly prompt reply, Charlie!

That got me going. At first I was troubled by seeing all of my new
threads labeled "Thread" in the log4j output (is this a bug?). I found
that by assigning my own names to the threads I could see each thread
executing as expected. I ended up with this:

t1 = Thread(target=JavaClassA.methodA, name='t1')
t2 = Thread(target=JavaClassB.methadB, name='t2')
t1.start()
t2.start()
t1.join()
t2.join()

Thanks again,

Ted


On Wed, Jul 8, 2009 at 6:46 PM, Charlie Groves<charlie.groves@...> wrote:

> Hi Ted,
>
> On Wed, Jul 8, 2009 at 1:32 PM, Ted Larson
> Freeman<freeman@...> wrote:
>> In my first attempt, using threads, "test.py" included code
>> like this:
>>
>> from threading import Thread
>> Thread(JavaClassA.methodA()).start()
>> Thread(JavaClassB.methodB()).start()
>
> Check out the docs for the Thread object:
> http://docs.python.org/library/threading.html#thread-objects  The
> first argument is the thread group, so you're setting the thread group
> for your threads with the results of methodA and methodB.  Since
> you're calling methodA and methodB to create arguments for Thread,
> they're run in the main thread.
>
> What you want to do is set the target of the Thread to the function or
> method you want invoked on the new thread, and then call start.  For
> example, the code below calls add on an ArrayList on a separate
> thread:
>
> Jython 2.5.0+ (trunk:6503:6505M, Jul 8 2009, 18:36:14)
> [Java HotSpot(TM) 64-Bit Server VM (Apple Inc.)] on java1.6.0_13
> Type "help", "copyright", "credits" or "license" for more information.
>>>> from threading import Thread
>>>> from java.util import ArrayList
>>>> l = ArrayList()
>>>> Thread(target=l.add, args=(5,)).start()
>>>> l
> [5]
>
> The args keyword arg is a tuple of positional arguments to pass to the
> target method.
>
> With your examples, you'd want to do
> Thread(target=JavaClassA.methodA).start() and
> Thread(target=JavaClassB.methodB).start().
>
> Hope this helps,
> Charlie
>
> ------------------------------------------------------------------------------
> Enter the BlackBerry Developer Challenge
> This is your chance to win up to $100,000 in prizes! For a limited time,
> vendors submitting new applications to BlackBerry App World(TM) will have
> the opportunity to enter the BlackBerry Developer Challenge. See full prize
> details at: http://p.sf.net/sfu/Challenge
> _______________________________________________
> Jython-users mailing list
> Jython-users@...
> https://lists.sourceforge.net/lists/listinfo/jython-users
>
>
>

------------------------------------------------------------------------------
Enter the BlackBerry Developer Challenge  
This is your chance to win up to $100,000 in prizes! For a limited time,
vendors submitting new applications to BlackBerry App World(TM) will have
the opportunity to enter the BlackBerry Developer Challenge. See full prize  
details at: http://p.sf.net/sfu/Challenge
_______________________________________________
Jython-users mailing list
Jython-users@...
https://lists.sourceforge.net/lists/listinfo/jython-users