This runs my xephyr windows for OBS and ensure that window manager and interesting tools are started

run_obs_config.py

import subprocess
import time
import sys
import os

# Start xephyr
xephyr = subprocess.Popen(
  "Xephyr -br -ac -noreset -screen 1920x1080 -dpi 300 :1".split()
  )

os.environ["DISPLAY"] = ":1"

i3 = subprocess.Popen(["i3"])

# Wait for i3 launch
time.sleep(1)

# Hide i3 bar
subprocess.run("i3 bar mode invisible".split())

# Runs the following background commands to populate
cmds = ["nix run nixpkgs.firefox -c firefox https://github.com/guibou/streamray",
"alacritty",
"nix run nixpkgs.xournal -c xournal"]

ps = [subprocess.Popen(cmd.split()) for cmd in cmds]

# move windows to their right place
subprocess.run("i3 move container to workspace 3".split())
subprocess.run("i3 move container to workspace 2".split())

os.environ["DISPLAY"] = ":0"

# Change the resolution
subprocess.run("xrandr -s 1920x1080".split())

try:
    i3.wait()
except KeyboardInterrupt:
    pass

for i in [i3, xephyr] + ps:
    i.kill()

# Restore resolution
subprocess.run("xrandr -s 3840x2160".split())