How can I log outside of main Flask module?
Even though this is a possible duplicate I want to write out a tiny bit of python logging knowledge.
DON'T pass loggers around. You can always access any given logger by logging.getLogger(<log name as string>)
. By default it looks like* flask uses the name you provide to the Flask
class.
So if your main module is called 'my_tool', you would want to do logger = logging.getLogger('my_tool')
in the Service
module.
To add onto that, I like to be explicit about naming my loggers and packages, so I would do Flask('my_tool')
** and in other modules, have sub level loggers like. logger = logging.getLogger('my_tool.services')
that all use the same root logger (and handlers).
* No experience, based off other answer.
** Again, don't use flask, dk if that is good practice
Edit: Super simple stupid example
Main Flask app
import sysimport loggingimport flaskfrom module2 import hiapp = flask.Flask('tester')handler = logging.StreamHandler(sys.stdout)handler.setFormatter(logging.Formatter( '%(asctime)s - %(name)s - %(levelname)s - %(message)s'))app.logger.addHandler(handler)app.logger.setLevel(logging.DEBUG)@app.route("/index")def index(): app.logger.debug("TESTING!") hi() return "hi"if __name__ == '__main__': app.run()
module2
import logginglog = logging.getLogger('tester.sub')def hi(): log.warning('warning test')
Outputs
127.0.0.1 - - [04/Oct/2016 20:08:29] "GET /index HTTP/1.1" 200 -2016-10-04 20:08:29,098 - tester - DEBUG - TESTING!2016-10-04 20:08:29,098 - tester.sub - WARNING - warning test
Edit 2: Messing with subloggers
Totally unneeded, just for general knowledge.
By defining a child logger, done by adding a .something
after the root logger name in logging.getLogger('root.something')
it gives you basiclly a different namespace to work with.
I personally like using it to group functionality in logging. So have some .tool
or .db
to know what type of code is logging. But it also allows so that those child loggers can have their own handlers. So if you only want some of your code to print to stderr
, or to a log you can do so. Here is an example with a modified module2
.
module2
import loggingimport syslog = logging.getLogger('tester.sub')handler = logging.StreamHandler(sys.stderr)handler.setFormatter(logging.Formatter('%(name)s - %(levelname)s - %(message)s'))log.addHandler(handler)log.setLevel(logging.INFO)def hi(): log.warning("test")
Output
127.0.0.1 - - [04/Oct/2016 20:23:18] "GET /index HTTP/1.1" 200 -2016-10-04 20:23:18,354 - tester - DEBUG - TESTING!tester.sub - WARNING - test2016-10-04 20:23:18,354 - tester.sub - WARNING - test