Removing handlers from python's logging loggers

Question

I am playing with Python\'s logging system. I have noticed a strange behavior while removing handlers from a Logger object in a loop. Namely, my for loop removes all but one

Answer 1

If you don't want to delete them all (thanks for the tip @CatPlusPlus):

testLogger.handlers = [
    h for h in testLogger.handlers if not isinstance(h, logging.StreamHandler)]

Answer 2

This isn't logger-specific behaviour. Never mutate (insert/remove elements) the list you're currently iterating on. If you need, make a copy. In this case testLogger.handlers = [] should do the trick.

Answer 3

instead of mutating undocumented .handler:

Option 1

logging.getLogger().removeHandler(logging.getLogger().handlers[0])

this way you remove exactly the preexisting handler object via offical api. Or to remove all handlers:

logger = logging.getLogger()
while logger.hasHandlers():
    logger.removeHandler(logger.handlers[0])

Option 2

logging.config.dictConfig(config={'level': logging.DEBUG, 'handlers': []}

Not only removes but prevents its creation. List root will have [] handlers

Answer 4

I've just found out that you can also do that within a logging .ini file, with the following block:

[logger_stpipe]
handlers=
propagate=1
qualname=stpipe

It basically deactivates all handlers for a given logger. But it's somewhat limited because you have to know the Logger's name in advance.