Run a python function with arguments from java using jython

Question

I want to execute a Python function which is located in one of my python projects from java by using jython. https://smartbear.com/blog/test-and-monitor/embedding-jython-in-java-applications/ is giving the sample code for the purpose. But in my scenario I got the following exception.

Exception in thread "main" Traceback (most recent call last): File "", line 1, in ImportError: No module named JythonTestModule

My scenario is as follows.

I have created a python module inside my python project(pythonDev) by using PyCharm(JythonTestModule.py) which contains the following function.

def square(value): return value*value

Then I created a sample java class in my java project(javaDev) and called the python module.

public static void main(String[] args) throws PyException{
   PythonInterpreter pi = new PythonInterpreter();
   pi.exec("from JythonTestModule import square");
   pi.set("integer", new PyInteger(42));
   pi.exec("result = square(integer)");
   pi.exec("print(result)");
   PyInteger result = (PyInteger)pi.get("result");
   System.out.println("result: "+ result.asInt());
   PyFunction pf = (PyFunction)pi.get("square");
   System.out.println(pf.__call__(new PyInteger(5)));
}

After running this java method the aforementioned exception is generated by the java program. I want to know what is the problem with this menioned code segments.

The JythonTestModule isn't found. is the JythonTestModule.py in the same directory as the Java project? It's most likely looking in the wrong directory for the module. — M. Goodman, Feb 11 '19 at 16:40
(I don't claim to know the answer, but). Since `JythonTestModule` is your module, how do you make sure the interpreter knows about it? Where does it look for modules other than system ones? — M. Prokhorov, Feb 11 '19 at 16:41
@M.Goodman the JythonTestModule is in my python project directory. — Shan Chathusanda Jayathilaka, Feb 11 '19 at 16:48
@M.Prokhorov do I need to add the JythonTestModule to the system modules? — Shan Chathusanda Jayathilaka, Feb 11 '19 at 16:49
Where is the java file located? Java execution will point from the home directory of the Java Main class. If that directory does not contain your python file it may not be finding the python file. — M. Goodman, Feb 11 '19 at 16:50
@M.Goodman my java file is in my java project. I put the JythonTestModule.py file to the directory that contains the java file. But the same exception occurred. — Shan Chathusanda Jayathilaka, Feb 11 '19 at 16:52
File tmpDir = new File("JythonTestModule.py"); boolean exists = tmpDir.exists(); System.out.println(exists); — M. Goodman, Feb 11 '19 at 16:57
Add that to the top of the main method to check if the compiler can see the file. If it returns false the file isn't directory visible. — M. Goodman, Feb 11 '19 at 16:59
@M.Goodman, I think he just needs to set `python.path` property for interpreter to his base dir. — M. Prokhorov, Feb 11 '19 at 17:00
@M.Prokhorov could you please explain me how to set the **python.path** property for the interpreter. — Shan Chathusanda Jayathilaka, Feb 11 '19 at 17:06
@ShanChathusandaJayathilaka, maybe [this reference](http://www.jython.org/javadoc/org/python/util/PythonInterpreter.html#initialize(java.util.Properties,%20java.util.Properties,%20java.lang.String[])) helps? — M. Prokhorov, Feb 11 '19 at 17:10
@M.Prokhorov is the **python.path** for the path to my python file? — Shan Chathusanda Jayathilaka, Feb 11 '19 at 17:18
@M.Prokhorov **python.path** is the directory path for the module file. Problem solved. — Shan Chathusanda Jayathilaka, Feb 11 '19 at 17:42

Shan Chathusanda Jayathilaka · Accepted Answer · 2019-02-22T08:35:33.230

As from the suggestions from the above comments section of this question, I have developed the solution to my question. Following code segment will demonstrate that. In this solution I have set the python.path as the directory path to my module file.

public static void main(String[] args) throws PyException{
       Properties properties = new Properties();
       properties.setProperty("python.path", "/path/to/the/module/directory");
       PythonInterpreter.initialize(System.getProperties(), properties, new String[]{""});
       PythonInterpreter pi = new PythonInterpreter();
       pi.exec("from JythonTestModule import square");
       pi.set("integer", new PyInteger(42));
       pi.exec("result = square(integer)");
       pi.exec("print(result)");
       PyInteger result = (PyInteger)pi.get("result");
       System.out.println("result: "+ result.asInt());
       PyFunction pf = (PyFunction)pi.get("square");
       System.out.println(pf.__call__(new PyInteger(5)));
    }

If you want to use multiple modules from the Jython, add the python.path as the parent directory path of all the modules in order to detect all the modules.

Run a python function with arguments from java using jython

1 Answers1