Question

So I am using subprocess to spawn a long running process through the web interface using Django. Now if a user wants to come back to the page I would like to give him the option of terminating the subprocess at a later stage.

How can do this? I implemented the same thing in Java and made a global singleton ProcessManager dictionary to store the Process Object in Memory. Can I do something similar in Python?

EDIT

Yes Singletons and a hash of ProcessManager is the way of doing it cleanly. Emmanuel’s code works perfectly fine with a few modifications.

Thanks

Answer 1

I think an easy way to implement Singleton pattern in python is via class attributes:

import subprocess

class ProcessManager(object):
    __PROCESS = None;

    @staticmethod
    def set_process(args):
        # Sets singleton process
        if __PROCESS is None:
            p = subprocess.Popen(args)
            ProcessManager.__PROCESS = p;
        # else: exception handling

    @staticmethod
    def kill_process():
        # Kills process
        if __PROCESS is None:
            # exception handling
        else:
            ProcessManager.__PROCESS.kill()

Then you can use this class via:

from my_module import ProcessManager

my_args = ...
ProcessManager.set_process(my_args)

...

ProcessManager.kill_process()

Notes:

• the ProcessManager is in charge of creating the process, to be symmetrical with its ending
• I don’t have enough knowledge in multi-threading to know if this works in multi-threading mode