Log from multiple python files into single log file in Python

You can do that using the logging module. Define this function in one of your base modules, and call it in every module you would like to log something.

import logging
def get_logger(name):
    log_format = '%(asctime)s  %(name)8s  %(levelname)5s  %(message)s'
    logging.basicConfig(level=logging.DEBUG,
                        format=log_format,
                        filename='dev.log',
                        filemode='w')
    console = logging.StreamHandler()
    console.setLevel(logging.DEBUG)
    console.setFormatter(logging.Formatter(log_format))
    logging.getLogger(name).addHandler(console)
    return logging.getLogger(name)

Then from every module you want to log from, call this function with the logger name you want, and all your modules would print to the same log file defined by the filename argument.

<base.py>
logger = get_logger('base')
logger.info('testing logger from module base')

<module2.py>
logger = get_logger('module2')
logger.info('testing logger from module module2')

<dev.log>
2017-08-11 00:34:00,361     base   INFO  testing logger from module base
2017-08-11 00:34:00,361     module2   INFO  testing logger from module module2

logging.basicConfig()

@Chen's answer is right. I'm providing a specific use case as follow:

Say you have two python files py1.py, py2.py that you want to import to your master file master.py.

#py1
import logging
def fun1():
    LOGGER = logging.getLogger(__name__)
    LOGGER.info('fun1 runs')

#py2
import logging
def fun2():
    LOGGER = logging.getLogger(__name__)
    LOGGER.info('fun2 runs')

#master.py
import py1
import py2
import logging
def main():
    logging.basicConfig(filename='log.log',level=logging.INFO)
    LOGGER = logging.getLogger("main")
    py1.fun1()
    py2.fun2()
    LOGGER.info('Master runs')

if __name__ == "__main__":
    main()

Then executing master.py will generate one single log.log file that contains logging from all modules (py1.py and py2.py).