Python Logging (function name, file name, line number) using a single file

Question

I am trying to learn how an application works. And for this I am inserting debug commands as the first line of each function's body with the goal of logging the function's name as well as the line number (within the code) where I send a message to the log output. Finally, since this application comprises of many files, I want to create a single log file so that I can better understand the control flow of the application.

Here is what I know:

1. for getting function name, I can use function_name.__name__ but I don't want to use the function_name (so that I could rapidly copy and paste a generic Log.info("Message") in the body of all functions). I know this could be done in C using __func__ macro but I am not sure about python.

2. for getting the filename and line number, I have seen that (and I believe that) my application is using Python locals() function but in a syntax that I am not completely aware of e.g.: options = "LOG.debug('%(flag)s : %(flag_get)s' % locals()) and I tried it using like LOG.info("My message %s" % locals()) which produces something like {'self': <__main__.Class_name object at 0x22f8cd0>}. Any input on this please?

3. I know how to use logging and add handler to it to log to a file but I am not sure if a single file can be used to record all log messages in correct order of function calls in the project.

I would greatly appreciate any help.

Thanks!

Answer 1

The correct answer for this is to use the already provided funcName variable

import logging
logger = logging.getLogger(__name__)
FORMAT = "[%(filename)s:%(lineno)s - %(funcName)20s() ] %(message)s"
logging.basicConfig(format=FORMAT)
logger.setLevel(logging.DEBUG)

Then anywhere you want, just add:

logger.debug('your message') 

Example output from a script I'm working on right now:

[invRegex.py:150 -          handleRange() ] ['[A-Z]']
[invRegex.py:155 -     handleRepetition() ] [[<__main__.CharacterRangeEmitter object at 0x10ba03050>, '{', '1', '}']]
[invRegex.py:197 -          handleMacro() ] ['\d']
[invRegex.py:155 -     handleRepetition() ] [[<__main__.CharacterRangeEmitter object at 0x10ba03950>, '{', '1', '}']]
[invRegex.py:210 -       handleSequence() ] [[<__main__.GroupEmitter object at 0x10b9fedd0>, <__main__.GroupEmitter object at 0x10ba03ad0>]]