Created

Embed URL

HTTPS clone URL

SSH clone URL

You can clone with HTTPS or SSH.

Download Gist

Flask logging example

View foo.log
1 2
A warning occurred (42 apples)
An error occurred
View foo.log
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
import logging
from logging.handlers import RotatingFileHandler
 
from flask import Flask
 
app = Flask(__name__)
 
@app.route('/')
def foo():
app.logger.warning('A warning occurred (%d apples)', 42)
app.logger.error('An error occurred')
app.logger.info('Info')
return "foo"
 
if __name__ == '__main__':
handler = RotatingFileHandler('foo.log', maxBytes=10000, backupCount=1)
handler.setLevel(logging.INFO)
app.logger.addHandler(handler)
app.run()

Thanks for the tip

Thanks dude

Lovely my friend! Thanks a lot for putting up this code chunk!

webus commented

Thanks!

Thanks its very useful :) Does flask provides a default logger or we have to provide one for it like RotatingFileHandler?

You can add this:

handler.setLevel(logging.ERROR)
formatter = logging.Formatter("%(asctime)s - %(name)s - %(levelname)s - %(message)s")

to include time and other info in the log item.

If you want line numbers as well in your logs, you can use this formatter:

    formatter = logging.Formatter(
        "[%(asctime)s] {%(pathname)s:%(lineno)d} %(levelname)s - %(message)s")
    handler = RotatingFileHandler(LOG_FILENAME, maxBytes=10000000, backupCount=5)
    handler.setLevel(logging.DEBUG)
    handler.setFormatter(formatter)
    app.logger.addHandler(handler)

If you also want to see the log messages emitted by Werkzeug in your log file, you can add the following:

    log = logging.getLogger('werkzeug')
    log.setLevel(logging.DEBUG)
    log.addHandler(handler)

thanks :)

Thank you

Thanks !

Prawyn commented

Thanks

Thanks

Muchas gracias..

I had to setLevel on app.logger as well to make it log from app.logger.info("...") and app.logger.debug("..."). If I only set the level of the handler, it would only log warn, error, and critical messages.

Here's what worked for me:

handler = TimedRotatingFileHandler('logs/foo.log', when='midnight', interval=1)
handler.setLevel(logging.DEBUG)
app.logger.addHandler(handler)
app.logger.setLevel(logging.DEBUG)

Thx~ It help me

Where will be the .log files be saved??

Thanks @KCzar -- I was having a devil of a time figuring out why my info messages were not being logged, setting level on app.logger fixed that problem.

It's very useful, thank you!

Thanks, useful code . It will be better if uniform field separator is used, this allows for log processing by automation tools . Eg
formatter = logging.Formatter(
"%(asctime)s | %(pathname)s:%(lineno)d |
%(funcName)s | %(levelname)s | %(message)s ")

the reason for set log level in app.logger in production is that app.logger set level of app.logger to logging.NOTSET(i.e. 0), and if app.debug is True then all log level above DEBUG will be logged to stderr(StreamHandler). However, if app.debuug is set to False then all the log level above logging.root.level(i.e. logging.WARNING). Check out the code about Flask logging.py file you will find what the problem is. Here is the link

Schlik commented

Thanks!

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Something went wrong with that request. Please try again.