Question

I’m writing an IRC bot in Python, due to the alpha nature of it, it will likely get unexpected errors and exit.

What’s the techniques that I can use to make the program run again?

Answer 1

You can use sys.exit() to tell that the program exited abnormally (generally, 1 is returned in case of error).

Your Python script could look something like this:

import sys

def main():
    # ...

if __name__ == '__main__':
    try:
        main()
    except Exception as e:
        print >> sys.stderr,  e
        sys.exit(1)
    else:
        sys.exit()

You could call again main() in case of error, but the program might not be in a state where it can work correctly again.
It may be safer to launch the program in a new process instead.

So you could write a script which invokes the Python script, gets its return value when it finishes, and relaunches it if the return value is different from 0 (which is what sys.exit() uses as return value by default).
This may look something like this:

import subprocess

command = 'thescript'
args = ['arg1', 'arg2']

while True:
    ret_code = subprocess.call([command] + args)

    if ret_code == 0:
        break