Calling python script from Java using runtime.getruntime.exec

Question

I have a java web development project, and want to call a python script to run in the background and then carry on with the java.

String command = "cmd.exe /c cd "C:\\path\\to\\py\\" && python script.py";
Process p = Runtime.getRuntime().exec(command);

Nothing seems to happen when i call this, but i need to change directory first as the script accesses files in its directory.

Thanks for your help

Edit:

Correct answer was adding start, this is my edited code

String command = "cmd.exe /c cd "C:\\path\\to\\py\\" && start python script.py";
Process p = Runtime.getRuntime().exec(command);

• mmmmmm: Could the python script run under jython? If so call it from java and run in a thread

Answer 1

Rather than using cmd to change the directory, you can set a process's working directory from the Java side. For example

ProcessBuilder pb = new ProcessBuilder("python", "script.py");
pb.directory(new File("C:\\path\\to\\py"));
Process p = pb.start();

Answer 2

Did you configure your environment to support "executable" python scripts?
If not, you should call it like this:

String command = "cmd.exe /c start python path\to\script\script.py";
Process p = Runtime.getRuntime().exec(command);

The start command runs the appropriate executable (in this case python interpreter), with its supplied arguments (in this case the script itself).