Example of implicit logging management.

exitLogger.py

#!/usr/bin/env python
# Time-stamp: <2015-03-30 15:21:15 ycopin>

from __future__ import division, print_function

"""
Example of implicit logging management.
"""

import sys, atexit, traceback


class ExitLogger(object):

    def __init__(self, pid, verbose=True):

        self.pid = pid
        self.status = 0
        self.msg = "Nothing to report"

        # Register methods for exceptions and exit
        sys.excepthook = self._excepthook
        atexit.register(self._atexit)

        self.verbose = verbose
        if self.verbose:
            print("From now on, all exits will be intercepted.")

    def __str__(self):

        return "ExitLogger: pid={}, status={}, msg={!r}".format(
            self.pid, self.status, self.msg)

    def critical_warning(self, status, msg):

        self.status = status
        self.msg = msg

    def _excepthook(self, exctype, value, tb):

        if self.verbose:
            print("Traceback:")
            traceback.print_tb(tb)

        self.status = 1
        self.msg = "{}: {}".format(exctype.__name__, value.message)

    def _atexit(self):

        print(self.__str__())


if __name__ == '__main__':

    import os

    try:
        case = int(sys.argv[1]) # Could fail
    except Exception as err:
        raise RuntimeError("Usage: {} 0|1|2".format(sys.argv[0]))

    logger = ExitLogger(os.getpid())

    if case == 0:               # Everything is going smoothly
        print("Everything is going smoothly.")
    elif case == 1:             # A warning is issued, but the code does not crash
        print("A critical warning is issued.")
        logger.critical_warning(2, "Warning")
    elif case == 2:             # An exception is raised somewhere
        print("Something went wrong.")
        raise RuntimeError("Error")