Launch an independent process with python

Question

Its a really simple question really, but I cant seem to find any solution.

I have a python script and I want to launch an independent daemon process. I want to call ym python script, launch this system tray dameon, do some python magic on a database file and quit, leaving the system tray daemon running.

I've tried os.system, subprocess.call, subprocess.Popen, os.execl, but it always keeps my script alive until I close the system tray daemon.

This sounds like it should be a simple solution, but I can't get anything to work.

EDIT: Solution for Windows: os.startfile() http://docs.python.org/library/os.html?highlight=startfile#os.startfile

Sometimes giving up and asking means you're just on the cusp of the answer.

Answer 1

You can use a couple nifty Popen parameters to accomplish a truly detached process on Windows (thanks to greenhat for his answer here):

import subprocess

DETACHED_PROCESS = 0x00000008
results = subprocess.Popen(['notepad.exe'],
                           close_fds=True, creationflags=DETACHED_PROCESS)
print(results.pid)

See also this answer for a nifty cross-platform version (make sure to add close_fds though as it is critical for Windows).

Answer 2

Solution for Windows: os.startfile()

Works as if you double clicked an executable and causes it to launch independently. A very handy one liner.

http://docs.python.org/library/os.html?highlight=startfile#os.startfile