How to Run a Python Program that Takes Command-Line arguments from within a Java Program

Question

I understand that to run another Java program from inside a Java program you use something like this:

Runtime.getRuntime().exec("/**A command goes here*/")

But how would I run a Python program that takes command-line arguments? More specifically, my Java program takes a file as a command-line argument. I then pass this file in to a Python program, which then produces another file in the same directory. I will be able to access this new file.

Can I simply call:

Runtime.getRuntime().exec("python /**directory_of_the_python_program arguments_for_program*/");

I'm also a bit confused about what goes inside "exec(...)".

PlasmaPower · Accepted Answer · 2014-03-19 02:51:34Z

2

Try capturing the standard output, so you can use print in python to output to this stream:

try {  
    Process p = Runtime.getRuntime().exec("python yourProgram.py thearg1 thearg2");  
    p.waitFor();
    InputStream stderr = proc.getOutputStream();
    InputStreamReader in = new InputStreamReader(stdout);
    BufferedReader reader = new BufferedReader(in);
    String line = null;
    while ((line = reader.readLine()) != null) {
        System.out.println("Python says: " + line);
    }
    int exitVal = proc.waitFor();
} catch (Exception e) {  
    e.printStackTrace();  
}

In your python program, to output to the Java program, use print like:

print 'Hi!'

To see what the Java program sent you, you can use sys.argv:

print 'The Java program sent me: ', str(sys.argv)

Note: I am not a python expert, and have not done much with it. Please tell me if I get some syntax wrong.

edited Mar 19, 2014 at 2:51

answered Mar 19, 2014 at 2:29

PlasmaPower

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