Automatically restart a Python program if it's killed

Question

I run a Python Discord bot. I import some modules and have some events. Now and then, it seems like the script gets killed for some unknown reason. Maybe because of an error/exception or some connection issue maybe? I'm no Python expert but I managed to get my bot working pretty well, I just don't exactly understand how it works under the hood (since the program does nothing besides waiting for events). Either way, I'd like it to restart automatically after it stops.

I use Windows 10 and just start my program either by double-clicking on it or through pythonw.exe if I don't want the window. What would be the best approach to verify if my program is still running (it doesn't have to be instant, the verification could be done every X minutes)? I thought of using a batch file or another Python script but I have no idea how to do such thing.

Thanks for your help.

Answer 1

You can write another python code (B) to call your original python code (A) using Popen from subprocess. In python code (B), ask the program to wait for your python code (A). If 'A' exits with an error code, recall it from B.

I provide an example for python_code_B.py

import subprocess

filename = 'my_python_code_A.py'
while True:
    """However, you should be careful with the '.wait()'"""
    p = subprocess.Popen('python '+filename, shell=True).wait()

    """#if your there is an error from running 'my_python_code_A.py', 
    the while loop will be repeated, 
    otherwise the program will break from the loop"""
    if p != 0:
        continue
    else:
        break

This will generally work well on Unix / Windows systems. Tested on Win7/10 with latest code update.

Also, please run python_code_B.py from a 'real terminal' which means running from a command prompt or terminal, and not in IDLE.

Answer 2

for problem you stated i prefer to use python subprocess call to rerun python script or use try blocks. This might be helpful to you. check this sample try block code:

try:
  import xyz # consider it is not exist or any error code
except:
  pass # go to next line of code to execute