You could try this way:

• Use Jython instead of CPython to write Python code http://www.jython.org.
• Integrate Jython code with Java code through Apache Bean Scripting Framework http://commons.apache.org/bsf/

If you definitely need to use CPython, then Apache Trift could be interesting for you: http://thrift.apache.org/ So you could make additional scalable abstraction layer and integrate your Java code with different languages (not only Python)

If you need a really low-level interface you could look at JNI http://java.sun.com/docs/books/jni/ for investigation. But I think it will take a lot of time to integrate your code with CPython using JNI.

You can make a one class java program with a thread never ending until you send from Python a notification to do so.

This way the lib would be kept in memory and accessible from your Python program.

This class could be like this (add your needed lib import/init) :

public class TestPy {

    private Thread thread;

    public void die() {
        synchronized (thread) {
            thread.interrupt();
        }    
    }

    public TestPy() {
        thread = new Thread(){
            public void run() {
                try {
                    while (!Thread.interrupted()) {
                        Thread.sleep(500);
                    }
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
            }
        };
        thread.start();    
    }

    public static void main(String[] args) {
        TestPy tp = new TestPy();
        GatewayServer server = new GatewayServer(tp);
        server.start();
    }
}

You would have to launch the java program, use the lib, and then use the die() method to kill the java program in Python :

gateway = JavaGateway()
do your stuff here using the lib
tp = gateway.entry_point
tp.die()