python: where to log an exception

Question

I looking for some "best-practice" advice.

In my Python app I am using exceptions for controlling the flow of my program. But I am not sure where I should log the exception. My gut feeling says I should log it closest to where the exception is raised. But that results in some rather clunky code:

def a_deeper_level_function():
 print("I am doing stuff, but it goes wrong. So raising.")
 
 # but I also want to log here with the same message.
 # so I put my msg in a separate variable to re-use it.
 msg = "this is the logging and exception message"
 _LOGGER.error(msg)
 raise Exception(msg)

Any thoughts appreciated!

Answer 1

In python, best practice is to use logging module to generate log file. And for exception handling always use try except block.

Try following approach:

import logging
def a_deeper_level_function():
 try:
 print("I am doing stuff, but it goes wrong. So raising.")
 # but I also want to log here with the same message.
 # so I put my msg in a separate variable to re-use it.
 msg = "this is the logging and exception message"
 _LOGGER.error(msg)
 raise Exception(msg) 
 except Exception as e:
 logging.info(e)
 

• user5386938: Or logging.exception(e). See stackoverflow.com/questions/5191830/…

Answer 2

If you manually raise exception and know where it's going to be, try finalize may work for you. It makes it easier to navigate between exceptions too.

def a_deeper_level_function():
 try:
 print("I am doing stuff, but it goes wrong. So raising.")
 msg = "this is the logging and exception message"
 raise Exception(msg) 
 finally:
 _LOGGER.error(msg)