RE: [Jython-users] Repeated instantiation of Python Objects in Java

[Robert D. <rdi...@tr...>]

Jeff,=20

Great suggestion on the "throws". One more thing, and BTW I appreciate
your help. Can I set python options before constructing the interpreter
using System.setProperty? For example:

        System.setProperty( "python.options.internalTablesImpl", "weak"
);
        System.setProperty( "python.options.showJavaExceptions", "true"
);
        System.setProperty( "python.options.showPythonProxyExceptions",
"true" );

Or do I need to put it in the registry?

R.

-----Original Message-----
From: Jeff Emanuel [mailto:JEm...@lg...]=20
Sent: Thursday, October 09, 2003 8:04 AM
To: Robert DiFalco
Subject: RE: [Jython-users] Repeated instantiation of Python Objects in
Java



Now I understand better.  You probably don't want to
redefine your classes, but it probably wouldn't have any
ill effects, it's just wasteful.  I would either define
all the classes a priori and omit the py.exec line or
create them the first time they were needed, either like
your second example, or you could try the eval, and if
that throws, then do the exec and eval again.  Then you
don't need to maintain redundant information that the interpreter
maintains anyway.

  PObject pyo=3Dnull;
  try { pyo=3Dpy.eval(desc.name+"()"); }
  catch (PyException ex) {
    // Should check that ex is a NameError.
    py.exec(desc.code);
    pyo=3Dpy.eval(desc.name+"()");
  }

Creating multiple instances shouldn't cause any leaks, especially since
you aren't assigning them to a variable in the interpreter.


-----Original Message-----
From: Robert DiFalco [mailto:rdi...@tr...]
Sent: Wednesday, October 08, 2003 9:41 PM
To: Jeff Emanuel
Subject: RE: [Jython-users] Repeated instantiation of Python Objects in
Java


Woops, that was a typo! The code instantiates objects. Like this:

 PythonInterpreter py =3D PythonInterp.getInstance();

 for ( awhile )
 {
     Descriptor desc =3D getRandomPythonImplementationOf =
MyInterface.class
);

     // exec the code (no main, just a single file single class, i.e.
foo.py)
     py.exec( desc.code );

     // construct an instance of the object (i.e. pyo =3D foo();)
     PyObject pyo =3D py.eval( desc.name + "()" ); // basically creates =
a
null constructor

     // cast it to an interface it implements
     MyInterface mi =3D (MyInterface)pyo.__tojava__( MyInterface.class =
);

     // call a method, garbage collector should clean up resources
     System.out.println( mi.toString() );
 }

Basically, I have a bunch of objects in python that I instantiate
multiple times from Java. I also do this all in the same interpreter.
I'm supposing that I only have to exec the code that contains the object
once. Is there any problems with exec'ing it more than once? Otherwise,
I suppose I will need to add a state variable something like this:

 PythonInterpreter py =3D PythonInterp.getInstance();

 for ( awhile )
 {
     Descriptor desc =3D getRandomPythonImplementationOf =
MyInterface.class
);

     // make sure it has only been executed once
     if ( !desc.hasCodeBeenExecuted )
     {
         // exec the code (no main, just a single file single class,
i.e. foo.py)
         py.exec( desc.getClassCode() );
         desc.hasCodeBeenExecuted =3D true;
     }

     // construct an instance of the object (i.e. pyo =3D foo();)
     PyObject pyo =3D py.eval( desc.getClassName() + "()" ); // =
basically
creates a null constructor

     // cast it to an interface it implements
     MyInterface mi =3D (MyInterface)pyo.__tojava__( MyInterface.class =
);

     // call a method, garbage collector should clean up resources
     System.out.println( mi.toString() );
 }
=20
Does that make sense? This is actually a rule server, there is really no
for loop like this. Basically, I look in the scheduler for different
types of rules to execute. These rules are python classes that implement
a Java Rule interface. The for loop was just to simulate what I am
doing.

R.

-----Original Message-----
From: Jeff Emanuel [mailto:JEm...@lg...]=20
Sent: Wednesday, October 08, 2003 8:25 PM
To: Robert DiFalco
Subject: RE: [Jython-users] Repeated instantiation of Python Objects in
Java


In principle, there shouldn't be any leaks with
the pseudocode you provided, but I'm not sure
what is supposed to do or what your goal is.
I think you need to specify what the Jython code
looks like.

PythonInterpreter.eval only takes a String and
you are passing it a PyCode.  I don't know why
you would exec and then eval the same code object.

Jython classes get cached, so if your code defines
a new class each time it is executed, you may have
a problem.  You can specify whether Jython uses soft
or weak references for the cache.  See the comment
in your Jython registry file where it sets
python.options.internalTablesImpl.


-----Original Message-----
From: Robert DiFalco
To: jyt...@li...
Sent: 10/8/2003 6:58 PM
Subject: [Jython-users] Repeated instantiation of Python Objects in Java

Is there anything I need to look out for here with regards to memory
leaks?

 PythonInterpreter py =3D PythonInterp.getInstance();

 for ( awhile )
 {
     PyCode code =3D getRandomPythonImplementationOf MyInterface.class =
);

     py.exec( code );

     PyObject pyo =3D py.eval( code );

     MyInterface mi =3D (MyInterface)pyo.__tojava__( MyInterface.class =
);

     System.out.println( mi.toString() );
 }


If the same code is returned and exec'd more than once, does the
interpreter know that it's been exec'd before? What actually happens
when I call "exec"? Should the code above have memory leaks?

TIA,

Robert


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