Python logging sys.exit('message')

Question

I followed this guide on how to take advantage of Python's logging module.

Now I each of my .py files get its logger by calling

logger = logging.getLogger(__name__)

The main .py file sets up logging reading a json configuration file.

import os
import json
import logging.config


def setup_logging(
    default_path='logging.json',
    default_level=logging.INFO,
    env_key='LOG_CFG'
):
    path = default_path
    value = os.getenv(env_key, None)
    if value:
        path = value
    if os.path.exists(path):
        with open(path, 'rt') as f:
            config = json.load(f)
        logging.config.dictConfig(config)
    else:
        logging.basicConfig(level=default_level)


setup_logging()

However, I have a lot of code that was written without proper logging that simply prints an error message before exiting.

# when error occurs
sys.exit('error message')

I'd like to know if there's a way to capture those errors, format them in the same way as other errors (with timestamp) and save them in the same a error.log file used by the logger.

This is my configuration file, logging.json

{
    "version": 1,
    "disable_existing_loggers": false,
    "formatters": {
        "simple": {
            "format": "%(asctime)s - %(name)s - %(levelname)s - %(message)s"
        }
    },

    "handlers": {
        "console": {
            "class": "logging.StreamHandler",
            "level": "DEBUG",
            "formatter": "simple",
            "stream": "ext://sys.stdout"
        },

        "info_file_handler": {
            "class": "logging.handlers.RotatingFileHandler",
            "level": "INFO",
            "formatter": "simple",
            "filename": "info.log",
            "maxBytes": 10485760,
            "backupCount": 20,
            "encoding": "utf8"
        },

        "error_file_handler": {
            "class": "logging.handlers.RotatingFileHandler",
            "level": "ERROR",
            "formatter": "simple",
            "filename": "errors.log",
            "maxBytes": 10485760,
            "backupCount": 20,
            "encoding": "utf8"
        }
    },

    "loggers": {
        "my_module": {
            "level": "ERROR",
            "handlers": ["console"],
            "propagate": false
        }
    },

    "root": {
        "level": "DEBUG",
        "handlers": ["console", "info_file_handler", "error_file_handler"]
    }
}

Answer 1

Since sys.exit is implemented by raising the SystemExit exception, you can catch the exception and log it:

import logging
import sys
import os

logging.basicConfig(level=logging.DEBUG)
logger = logging.getLogger('example')

def function_will_exit():
    sys.exit('some error log')

try:
    function_will_exit()
except SystemExit as e:
    # this log will include traceback
    logger.exception('function_will_exit failed with exception')
    # this log will just include content in sys.exit
    logger.error(str(e))

    # if you don't need exception traceback from Python
    # os._exit(1)
    raise