I have a Python3 program, B.py which I need to have run continuously. B.py may throw an exception and when that happens, I'd like to have it exit/shutdown. Pythong3 program A.py should watch and if B.py has exited, should start another instance of B.py.
I've searched SO and can't find a nice clean way. I'm not sure that writing the PID to a file is the best way to go (could the file be locked, for example?).
As a side note, I'm a python noobie, so please be as explicit as possible.
The programs shown below are meant to demonstrate a very simple way of accomplishing your goal.
The entire purpose of program A is to keep running program B over and over again. The shell argument is specified in this example so that it will easily run on both Windows and Linux, assuming program B has permission to execute. Feel free to expand on this program as you have need to.
#! /usr/bin/env python3
import subprocess
def main():
while True:
subprocess.run('B.py', shell=True)
if __name__ == '__main__':
main()
This program should be replaced with your own, but it demonstrates a running program that crashes with random exceptions. The EXCEPTIONS strings is copied straight from the documentation, and the rest of the code should be easy to follow. The only use for this program is for testing program A.
#! /usr/bin/env python3
import builtins
import random
import time
EXCEPTIONS = '''\
BaseException
+-- SystemExit
+-- KeyboardInterrupt
+-- GeneratorExit
+-- Exception
+-- StopIteration
+-- StopAsyncIteration
+-- ArithmeticError
| +-- FloatingPointError
| +-- OverflowError
| +-- ZeroDivisionError
+-- AssertionError
+-- AttributeError
+-- BufferError
+-- EOFError
+-- ImportError
+-- ModuleNotFoundError
+-- LookupError
| +-- IndexError
| +-- KeyError
+-- MemoryError
+-- NameError
| +-- UnboundLocalError
+-- OSError
| +-- BlockingIOError
| +-- ChildProcessError
| +-- ConnectionError
| | +-- BrokenPipeError
| | +-- ConnectionAbortedError
| | +-- ConnectionRefusedError
| | +-- ConnectionResetError
| +-- FileExistsError
| +-- FileNotFoundError
| +-- InterruptedError
| +-- IsADirectoryError
| +-- NotADirectoryError
| +-- PermissionError
| +-- ProcessLookupError
| +-- TimeoutError
+-- ReferenceError
+-- RuntimeError
| +-- NotImplementedError
| +-- RecursionError
+-- SyntaxError
| +-- IndentationError
| +-- TabError
+-- SystemError
+-- TypeError
+-- ValueError
| +-- UnicodeError
| +-- UnicodeDecodeError
| +-- UnicodeEncodeError
| +-- UnicodeTranslateError
+-- Warning
+-- DeprecationWarning
+-- PendingDeprecationWarning
+-- RuntimeWarning
+-- SyntaxWarning
+-- UserWarning
+-- FutureWarning
+-- ImportWarning
+-- UnicodeWarning
+-- BytesWarning
+-- ResourceWarning
'''
def main():
time.sleep(random.uniform(1, 9))
lines = EXCEPTIONS.splitlines()
names = [line.rsplit(None, 1)[-1] for line in lines]
raise getattr(builtins, random.choice(names))()
if __name__ == '__main__':
main()
