Question

I am working on a big Java project, where Jython scripts are interpreted from Java code. For a reason I have not yet figured out, nothing works in the Jython script unless functions, class, variables, are declared all as global.
In an attempt to track down this problem, I have narrowed the issue down to this. Below are :

• A Jython script script.py which runs well when launched with java -jar jython.jar script.py
• A Java main class Interpreter.java which uses Jython 2.2 methods to try and interpret the Jython script given above

Python script :

#global aFunction # uncommenting this makes the script work from Java

def main():
    aFunction()


def aFunction():
    print 'aFunction() called'


main()

Java class :

import java.io.File;

import org.python.core.PyException;
import org.python.core.PyStringMap;
import org.python.core.PySystemState;


public class Interpreter {

    public static void main(final String[] args) {
        final PyStringMap localNameSpace = new PyStringMap();
        final PyStringMap globalNameSpace = new PyStringMap();

        final File scriptFile = new File("../../jython/script.py");       
        PySystemState.initialize();

        try {
            org.python.core.__builtin__.execfile(scriptFile.getAbsolutePath(), globalNameSpace, localNameSpace);
        } catch (final PyException pyException) {
            pyException.printStackTrace();
        }

    }

}

Here is the error I get when running the Java class.

Traceback (innermost last):
  File "/opt/coflight/axel/workspace/essais/../../jython/script.py", line 12, in ?
  File "/opt/coflight/axel/workspace/essais/../../jython/script.py", line 5, in main
NameError: aFunction

Any ideas on how to correct the Java class so that the interpreter can run the Jython script ? Thanks !

Answer 1

I can’t explain the error that you get, but I was able to make it work by using PythonInterpreter:

org.python.util.PythonInterpreter interp = new org.python.util.PythonInterpreter();
String scriptname = "script.py"; 
interp.execfile(scriptname);