How to call a python program in java using Runtime

Question

I want to call a python program with arguments from java. But my output is a blank. The code is here.

Python code is here:

import sys

print(sys.argv[1])

And the java code is here:

public class PrintNumber{
    public static void main(String[] args){
        Process proc;
        try {
            proc = Runtime.getRuntime().exec("python ../pythonProgram/pythonProgram/PrintN.py 30");
            BufferedReader in = new BufferedReader(new InputStreamReader(proc.getInputStream()));
            String line = null;
            while ((line = in.readLine()) != null) {
                System.out.println(line);
            }
            in.close();
            proc.waitFor();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }   
}

I want to output 30, could somebody tell me where is the mistake?

Maybe the Python script is not found. To investigate you might read from proc.getErrorStream instead to see any error. — SubOptimal
– SubOptimal, Commented Nov 18, 2019 at 8:51

user12297736 · Accepted Answer · 2019-11-22 08:55:47Z

0

You can try it out:

String command = "python /c start python ../pythonProgram/pythonProgram/PrintN.py";

int param = 30;

proc = Runtime.getRuntime().exec(command + param);

Reference: Run Python script by Java

answered Nov 22, 2019 at 8:55

user12297736

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1 Comment

シュクゴチ Over a year ago

I kinda solve this problem, my issue is that I cannot run python code which imports a third-party library. So I need to find the full name of my python, which means I should code "which python" in terminal first, and then write down the full path. In this case, instead of "python ../pythonProgram/pythonProgram/PrintN.py 30", I should write down "/Users/archer/anaconda3/bin/python ../pythonProgram/pythonProgram/PrintN.py 30" and the first parameter is the outcome after "which python"

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