Python global logging

Question

How do I make a Logger global so that I can use it in every module I make?

Something like this in moduleA:

import logging
import moduleB

log = logging.getLogger('')

result = moduleB.goFigure(5)
log.info('Answer was', result)

With this in moduleB:

def goFigure(integer):
    if not isinstance(integer, int):
        log.critical('not an integer')
    else:
        return integer + 1

Currently, I will get an error because moduleB does not know what log is. How do I get around that?

score 30 · Accepted Answer · answered Jun 21 '12 at 05:14

30

You could make your own logging "module" which instantiates the logger, than have all of your code import that instead. Think:

logger.py:

import logging
log = logging.getLogger('')

codeA.py:

from logger import log
log.info('whatever')

codeB.py:

from logger import log
log.warn('some other thing')

answered Jun 21 '12 at 05:14

Haldean Brown

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This solution worked like a charm even with custom logger setup. – Centurion Jul 05 '17 at 12:21
1

Does this work when adding logger adapters? Say I add an adapter in codeA will it be picked up in codeB? – Simon Melouah Sep 19 '18 at 16:37

score 9 · Answer 2 · edited Nov 24 '16 at 10:54

Creating a global logger which can be used to

create a new log file or
returns logger for a global log file.

Create a module called called myLogger.py : This will have the log creation code

myLogger.py:

import logging

def myLog(name, fname = 'myGlobalLog.log'):
'''Debug Log'''                                                                                                 
    logger = logging.getLogger(name);                                                                               
    logger.setLevel(logging.DEBUG)                                                                                  
    fhan = logging.FileHandler(fname)                                                                               
    fhan.setLevel(logging.DEBUG)                                                                                    
    logger.addHandler(fhan)                                                                                         
    formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')                           
    fhan.setFormatter(formatter)
    '''comment this to enable requests logger'''                                                                    
    #logger.disabled = True
    return logger

Now to create a new log in your module say A.py

from myLogger import myLog
log = myLog(__name__, 'newLog.log')
log.debug("In new log file")

Thus you have to pass the file name along while getting the logger.

To use the global logger in A.py:

from myLogger import myLog
log = myLog(__name__)
log.debug("In myGlobalLog file")

Need not pass the file name in this case as we gonna use the global log.

score 2 · Answer 3 · answered Jun 21 '12 at 05:13

A module has by default only access to builtin functions and builtin constants. For all other variables, functions... you have to use the keyword import.

Now for your concrete example, you can import the log-variable of moduleA in modulesB like this:

from moduleA import log

The following would be equivalent because the logging-module returns the same instance of the logger that was returned to moduleA:

import logging
log = logging.getLogger('')

Another solution for you could be to use the default-logger of the logging module like this:

logging.info("Hello")

Python global logging

3 Answers3

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