jpyll

Java-Python Linker Library

The library is aimed to reduce the effort to integrate the Python environment to the Java ecosystem.

With this library you will able to call your Python scripts from your Java apps and retrieve all the messages that are produced by your Python program.

Quick Guide

Example 1

1. Your Python Environment

Consider that you have your standard Python environment installed at: C:\Python311

2. Your Python Script

For instance, consider that you have a Python script called print_numbers_v1.py which is intented to print the first 10 numbers starting at 1:

# [C:/Users/Markdown/print_numbers_v1.py]

for i in range(1, 11):
    print(i)

And imagine that your python file is stored in C:/Users/Markdown/print_numbers_v1.py.

From you Java app, you can invoke the Python environment to execute your script and print the outputs produced by Python in whis way:

public class Test
{
    public static void main(String[] args)
    {
        try
        {
            PythonEnvironment pyenv = new PythonEnvironment("C:/Python311",
                                                            "C:/Python311/python.exe");
            PythonScript ps = new PythonScript("C:/Users/Markdown/print_numbers_v1.py");
            PythonListener listener = new PythonListener()
            {
                @Override
                public void onReady()
                {
                    System.out.println("Python Environment Ready!");
                }

                @Override
                public void onMessage(String message)
                {
                    System.out.println(message);                    
                }

                @Override
                public void onFinish()
                {
                    System.out.println("Python Process Ended.");
                }
                
                @Override
                public void onException(Exception e)
                {
                    e.printStackTrace();
                }
            };
            JPythonLinker jpyl = new JPythonLinker();
            jpyl.runScript(pyenv, ps, listener);
        }
        catch (Exception ex
        {
            ex.printStackTrace();
        }
    }
}

JSON Alternative

As an alternate way, jpyll is able to configure the Python environment and script information from JSON files as follows.

Python Environment file

Suppose that you have your configuration in path C:/Users/Markdown/python_env.json with the next content:

{
    "pythonPath"    :  "C:/Python311",
    "pythonBinPath" :  "C:/Python311/python.exe"
}

You can create the PythonEnvironment object as:

PythonEnvironment pyenv = PythonEnvironment.fromFile("C:/Users/Markdown/python_env.json");

Consequently, the script configuration file (C:/Users/Markdown/script01.json) content can be as follows:

{
    "shortName"     : "Example01",
    "description"   : "Script which prints the first 10 int numbers.",
    "filePath"      : "C:/Users/Markdown/print_numbers.py",
    "action"        : "",
    "arguments"     : []
}

And, the PythonScript object can be created as following:

PythonScript ps = PythonScript.fromFile("C:/Users/Markdown/script01.json");

Example 2

In this example, you have a second Python Script which prints the first N integer numbers, where N is a value passed as an argument to the script. In this example, the Python script code is as follows:

# [C:/Users/Markdown/print_numbers_v2.py]
import sys

try:
    
    max_value = int(sys.argv[1])
    print('Argument Received [max_value=%d]' % max_value)
    for i in range(1, max_value + 1):
        print(i)

except Exception as e:
    print(str(e))
except Warning as w:
    print(str(w))
except RuntimeWarning as rw:
    print(str(rw))

And this is your script configuration file stored in [C:/Users/Markdown/script02.json]:

{
    "shortName"     : "Example02",
    "description"   : "Script which prints the first N int numbers specified by the max_value argument.",
    "filePath"      : "C:/Users/Markdown/print_numbers_v2.py",
    "action"        : "",
    "arguments"    :   [
                            {
                                "name" : "max_value",
                                "type" : "Int",
                                "value": "50000"
                            }
                        ]
}

By considering the environment path such as in Example 1, the procedure to run your script from Java is as follows:

public class Test
{
    public static void main(String[] args)
    {
        try
        {
            PythonEnvironment pyenv = PythonEnvironment.fromFile("C:/Users/Markdown/python_env.json");
            PythonScript ps = PythonScript.fromFile("C:/Users/Markdown/script02.json");
            PythonListener listener = new PythonListener()
            {
                @Override
                public void onReady()
                {
                    System.out.println("Python Environment Ready!");
                }

                @Override
                public void onMessage(String message)
                {
                    System.out.println(message);                    
                }

                @Override
                public void onFinish()
                {
                    System.out.println("Python Process Ended.");
                }
                
                @Override
                public void onException(Exception e)
                {
                    e.printStackTrace();
                }
            };
            JPythonLinker jpyl = new JPythonLinker();
            jpyl.runScript(pyenv, ps, listener);
        }
        catch (Exception ex)
        {
            ex.printStackTrace();
        }
    }
}