Flask不打印sys.stdout.write消息

Question

I am running the flask app from this link using the command python app.py .

More logs printed using, sys.stdout.write are not printed on the console. However using logging.StreamHandler works for redirecting messages to stdout.

It works,

import logging
import logging.handlers
logger = logging.getLogger('kumologging')
logger.setLevel(logging.DEBUG)
ch = logging.StreamHandler()
logger.addHandler(ch)
logger.info("hey, i am from logger obj")

It doesn't work

import sys
sys.stdout.write("hey, i am from stdout")

Does flask override sys.stdout file descriptor, redirecting the logs elsewhere?

Answer 1

afaik flasks app.run() uses the gunicorn web package

I believe gunicorn is the one that is actually redirecting your output

the output might be in /var/log/gunicorn/error.log (not sure where it would be on windows :/)

or its possible sys.stdout is just not flushing its buffer, try sys.stdout.flush() after writting to it