Start a background process in Python

Detaching the process

To run a process in the background, we must detach it from the parent. You wouldn't want it to stop the second its parent takes a nap, right? 'close_fds=True' lets Python handle this, and 'DETACHED_PROCESS flag' does the magic on Windows.

In a Windows environment, use 'DETACHED_PROCESS' to start configuring the process like a backstage rock band:

import subprocess
import sys

DETACHED_PROCESS = 0x00000008

# Instead of "Hi, World!" it's "Bye, Console!"
if sys.platform == 'win32':
    subprocess.Popen(['command', 'arg1', 'arg2'], creationflags=DETACHED_PROCESS)
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Remember, this only detaches the consoles on Windows, not the groupies or stage hands.

The old-school way: os.system

Sometimes, os.system() can be used instead of subprocess. It's great for short, sweet, and not-so-important tasks.

import os

# Look mom, no hands! (& is for background processes in Unix)
os.system("command arg1 arg2 &")
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However, this method ain’t good for ain’t Windows. The os.system() method leaves you exposed and limits flexibility, asking you to bare it all, rather than neatly packaging it like subprocess.

Long run with Daemon

For long-lived tasks, Python contains daemon threads. Their only mission is to run in the background until all non-daemon threads bow down.

import threading

def background_task():
    # This one's in for the long run, like a royal guard!
    pass

daemon_thread = threading.Thread(target=background_task)
daemon_thread.setDaemon(True)
daemon_thread.start()
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Flexibility with subprocess

While os.system() seems easy, subprocess is like a multitool, offering creativity, security, and even standard input/output/error stream control.

For instance, with subprocess, you don't need to switch directories before running the command. Just pass cwd as an argument. You can also set environment variables for the new process using the env argument.

NOTE: Using subprocess.communicate() is like looking at your watch every second. It will wait for the process to end, which is pretty boring, right?

Safety first

Safety lies in sanitizing the inputs. Always double-check, especially when inputs are externally derived or user-generated. You wouldn't want to execute something nasty, right?

And, don't forget, official Python documentation is like your manual or encyclopedia. Always keep it handy.