Modern form of self-modifying code

erc_notifier.py

#!/usr/bin/env python3
import sys, os, subprocess, signal
#usage $~/lab/erc-notifier.py title message
### pop up the first notify window, and kill it when pop up the second notify window
controler=0
previous_pid=0
if controler == 0:
    p0=subprocess.Popen(['/home/jusss/lab/notifier.py', sys.argv[1], sys.argv[2]], shell=False)
    ### just replace once! sed -i '0,/a/ s//e/' example
    os.system("sed -i -e '0,/controler=0/ s//controler=1/' ~/lab/erc-notifier.py")
    os.system("sed -i -e '0,/previous_pid=0/ s//previous_pid=" + str(p0.pid) + "/' ~/lab/erc-notifier.py")
if controler == 1:
    try:
        ### consider if you click ok, and then process exit, so the process won't exist anymore
        os.kill(previous_pid,signal.SIGTERM)     
    except Exception as e:
        print(e)
    p=subprocess.Popen(['/home/jusss/lab/notifier.py', sys.argv[1], sys.argv[2]], shell=False)
    os.system("sed -i -e '0,/previous_pid=" + str(previous_pid) + "/ s//previous_pid=" + str(p.pid) + "/' ~/lab/erc-notifier.py")

Recently, a rookie came to our IRC channel and asked for help, because they extended an IRC client for desktop notifications, and "it does not work" (that was the full description of the problem). After some work, we got them to paste the code they wrote.