Making Python loggers output all messages to stdout in addition to log file

All logging output is handled by the handlers; just add a logging.StreamHandler() to the root logger.

Here's an example configuring a stream handler (using stdout instead of the default stderr) and adding it to the root logger:

import logging
import sys

root = logging.getLogger()
root.setLevel(logging.DEBUG)

handler = logging.StreamHandler(sys.stdout)
handler.setLevel(logging.DEBUG)
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
handler.setFormatter(formatter)
root.addHandler(handler)

The simplest way to log to stdout:

import logging
import sys
logging.basicConfig(stream=sys.stdout, level=logging.DEBUG)

You could create two handlers for file and stdout and then create one logger with handlers argument to basicConfig. It could be useful if you have the same log_level and format output for both handlers:

import logging
import sys

file_handler = logging.FileHandler(filename='tmp.log')
stdout_handler = logging.StreamHandler(sys.stdout)
handlers = [file_handler, stdout_handler]

logging.basicConfig(
    level=logging.DEBUG, 
    format='[%(asctime)s] {%(filename)s:%(lineno)d} %(levelname)s - %(message)s',
    handlers=handlers
)

logger = logging.getLogger('LOGGER_NAME')