Question

I am using the logging module in python as:

import logging, sys
logger= logging.getLogger(__file__)
logging.basicConfig(stream = sys.stderr, level=logging.DEBUG, format='%(filename)s:%(lineno)s %(levelname)s:%(message)s')
logger.debug("Hello World")

Now, after I have set the basic configuration on line 3, I want to have a command line argument that can change the output stream from sys.stderr to a file.

I have read the doc and it says that if both filename and stream are present at the same time, the stream is ignored.

Now, I wanna know how do change the stream to a file after I have already done the basicConfig thing in line 3?

Answer 1

If you look in the Python sources for logging/__init__.py, you’ll see that basicConfig() sets the handlers on the root logger object by calling addHandler(). If you want to start from scratch, you could remove all existing handlers and then call basicConfig() again.

# Example to remove all root logger handlers and reconfigure. (UNTESTED)
import logging

# Remove all handlers associated with the root logger object.
for handler in logging.root.handlers[:]:
    logging.root.removeHandler(handler)

# Reconfigure logging again, this time with a file.
logging.basicConfig(filename = 'myfile.log', level=logging.DEBUG, format='%(filename)s:%(lineno)s %(levelname)s:%(message)s')