How can I run roscore from python ?

edit

If you want to use the subprocess approach you should make sure that all processes are killed cleanly.

import subprocess
import shlex
import sys
import signal
import psutil

def kill_child_processes(parent_pid, sig=signal.SIGTERM):
    try:
        parent = psutil.Process(parent_pid)
        print(parent)
    except psutil.NoSuchProcess:
        print("parent process not existing")
        return
    children = parent.children(recursive=True)
    print(children)
    for process in children:
        print("try to kill child: " + str(process))
        process.send_signal(sig)

class Roscore(object):
    """
    roscore wrapped into a subprocess.
    Singleton implementation prevents from creating more than one instance.
    """
    __initialized = False
    def __init__(self):
        if Roscore.__initialized:
            raise Exception("You can't create more than 1 instance of Roscore.")
        Roscore.__initialized = True
    def run(self):
        try:
            self.roscore_process = subprocess.Popen(['roscore'])
            self.roscore_pid = self.roscore_process.pid  # pid of the roscore process (which has child processes)
        except OSError as e:
            sys.stderr.write('roscore could not be run')
            raise e
    def terminate(self):
        print("try to kill child pids of roscore pid: " + str(self.roscore_pid))
        kill_child_processes(self.roscore_pid)
        self.roscore_process.terminate()
        self.roscore_process.wait()  # important to prevent from zombie process
        Roscore.__initialized = False

Usage is like follows:

roscore = Roscore()
roscore.run()
roscore.terminate()

I think this is the ROS way to do it:

import roslaunch
uuid = roslaunch.rlutil.get_or_generate_uuid(options_runid=None, options_wait_for_master=False)
roslaunch.configure_logging(uuid)
launch = roslaunch.parent.ROSLaunchParent(uuid, roslaunch_files=[], is_core=True)
launch.start()
#  --- your code ---
launch.shutdown()

You can specify your launch files as a list of string in the ROSLaunchParent constructor. Check the doc if needed.

Usually, a ROS application is started by running the roslaunch command in the command line and providing it a launch file. This tutorial covers the basics of roslaunch, but there are more in depth examples else where. When roslaunch is used, it starts the roscore and any nodes that are listed in the roslaunch.

Does this answer your question? If not, could you explain a little more about what you're trying to do?