Jython code throws ImportError when invoked from a Java jar

[Debashish Chakrabarty]

Hello Ranchers,

I am trying to invoke a Python script from a Spring Boot application which is bundled as a JAR. I added Maven dependency for Jython Standalone JAR. The following code throws error at the execfile call (the code is able to get the Python file as input stream correctly):

ByteArrayOutputStream out = new ByteArrayOutputStream();
ByteArrayOutputStream err = new ByteArrayOutputStream();
String[] result = new String[2];
Properties preprops = System.getProperties();

Properties props = new Properties();
//props.put("python.path", "?");
props.put("python.console.encoding", "UTF-8");
props.put("python.security.respectJavaAccessibility", "false"); 
props.put("python.import.site", "false");

PythonInterpreter.initialize(preprops, props, new String[0]);
PythonInterpreter pyInterpreter = new PythonInterpreter();

try {
    Resource resource = new ClassPathResource("myPythonFile.py");
    pyInterpreter.set("args", "a string argument");
    pyInterpreter.setOut(out);
    pyInterpreter.setErr(err);
    pyInterpreter.execfile(resource.getInputStream());

    result[0] = out.toString();// reading the output
    result[1] = err.toString();// reading the error
} catch (Exception e) {
    logger.error("Error in code: ", e);
} finally {
    try {
        if (out != null)
            out.close();
        if (err != null)
            err.close();
        pyInterpreter.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Error thrown:

org.python.core.PyException: null
        at org.python.core.Py.ImportError(Py.java:334) ~[jython-standalone-2.7.1.jar!/:na]
        at org.python.core.imp.import_first(imp.java:879) ~[jython-standalone-2.7.1.jar!/:na]
        at org.python.core.imp.import_module_level(imp.java:964) ~[jython-standalone-2.7.1.jar!/:na]
        at org.python.core.imp.importName(imp.java:1057) ~[jython-standalone-2.7.1.jar!/:na]
        at org.python.core.ImportFunction.__call__(__builtin__.java:1280) ~[jython-standalone-2.7.1.jar!/:na]
        at org.python.core.PyObject.__call__(PyObject.java:450) ~[jython-standalone-2.7.1.jar!/:na]
        at org.python.core.__builtin__.__import__(__builtin__.java:1232) ~[jython-standalone-2.7.1.jar!/:na]
        at org.python.core.imp.importOne(imp.java:1076) ~[jython-standalone-2.7.1.jar!/:na]
        at org.python.pycode._pyx1.f$0(<iostream>:251) ~[na:na]
        at org.python.pycode._pyx1.call_function(<iostream>) ~[na:na]
        at org.python.core.PyTableCode.call(PyTableCode.java:171) ~[jython-standalone-2.7.1.jar!/:na]
        at org.python.core.PyCode.call(PyCode.java:18) ~[jython-standalone-2.7.1.jar!/:na]
        at org.python.core.Py.runCode(Py.java:1614) ~[jython-standalone-2.7.1.jar!/:na]
        at org.python.util.PythonInterpreter.execfile(PythonInterpreter.java:296) ~[jython-standalone-2.7.1.jar!/:na]
        at org.python.util.PythonInterpreter.execfile(PythonInterpreter.java:291) ~[jython-standalone-2.7.1.jar!/:na]

My Python script is using the following imports:

import sys
import argparse
import re
import json

I assume that it is probably happening because I am unable to set the property "python.path", but I am not sure how could I do that (the Jython JAR is being bundled under BOOT-INF/lib by Spring Boot). Also, there is no way for me to actually provide an absolute path for the Python installation (if that is what Jython expects) as the JAR would be deployed on a PaaS where file-system access is not enabled.

Appreciate your help in solving this.