Call Python from Java

Question

I want to call a python script from Java. My python version is 2.5 and Java is 6.

My current code:

try{
 Process p= Runtime.getRuntime().exec("path/dirs/file.py");
 p.waitFor();
 } catch (InterruptedException ex){
 System.out.println(ex.getMessage());}
 }

The error I receive is:

Java.IO.IOException: Cannot run program filename: CreateProcess error = 193, %1 is not a valid Win32 application

• Display Name: Windoze doesn't understand #!... in script files. There's no way it would work on all Windoze systems, you'd have to explicitly invoke Python executable and put script as argument to it.

Answer 1

Try to use PrecessBuilder -

try{
 String prg = "import sys\nprint int(sys.argv[1])+int(sys.argv[2])\n";
 BufferedWriter out = new BufferedWriter(new FileWriter("test1.py"));
 out.write(prg);
 out.close();
 int number1 = 10;
 int number2 = 32;
 ProcessBuilder pb = new ProcessBuilder("python","test1.py",""+number1,""+number2);
 Process p = pb.start();
 BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));
 int ret = new Integer(in.readLine()).intValue();
 System.out.println("value is : "+ret);
}catch(Exception e){System.out.println(e);}

See here from more detail.

Answer 2

The easiest way to integrate a Java application with Python is to use Jython.

I have used this successfully in the past to build scriptable java applications before we had access to Nashorn and it's ilk.

Answer 3

try this, This works for me

test_python.py

def addition(a,b):
 c=a+b
 return(c)

interpreterPython.java

package com.pythonconnect;
import org.python.util.PythonInterpreter;
public class interpreterPython {
 public static void main(String[] args) {
 System.setProperty("python.cachedir.skip", "true");
 PythonInterpreter interpreter = new PythonInterpreter();
 interpreter.execfile("test_python.py");
 interpreter.exec("print(addition(7,8))");
 }
}

Answer 4

You can run only a windows executable like a EXE or BAT file using the Runtime.exec function. You need to find a way to instantiate the Python interpreter and then give the file name using a .BAT File.