Not able to print custom log level on stream handlers using logging module in python3.6

Question

Below is the function in __init__.py file which means this part of code always run when code is executed

import logging
def log_setup():

    logging.TRACE = 5
    logging.addLevelName(5, 'TRACE')
    def trace(obj, message, *args, **kws):
        obj.log(logging.TRACE, message, *args, **kws)
    logging.Logger.trace = trace
    logging.trace = trace
    root = logging.getLogger("TEST")
    root.setLevel(5)
    ch = logging.StreamHandler()
    ch.setFormatter(f)
    ch.setLevel(5)
    root.handlers = []
    root.addHandler(ch)

I am having below code in one of the library say xyz.py

import logging
log = logging.getLogger("TEST."+__name__)
if log.trace:
    print("***ELLO***", log.getEffectiveLevel())
    print("***ELLO***", log.isEnabledFor(logging.DEBUG))
    print("***ELLO***", log.isEnabledFor(logging.TRACE))
    log.trace("Hey Statement printed")

When I am calling via script, I am not able to get the log.trace printed. Interestingly, For log.isEnabledFor(logging.TRACE) is always returning False.

Not sure what i am missing here

Below is the output

***ELLO*** 10
***ELLO*** True
***ELLO*** False

Can't reproduce. If I take your code, enhance it by defining the formatter in log_setup() (e.g. f = logging.Formatter('{message}', style='{') and calling log_setup() in __init__.py on module level, I get Hey Statement printed in the terminal. Double-check the code, maybe you forgot to call log_setup()? — hoefling
– hoefling, Commented Aug 6, 2018 at 10:42
@hoefling: Script from where I was calling was having call as root = logging.getLogger("TEST"). I changed this command to root = logging.getLogger("TEST."+__name) and it worked. Not sure why — Sumit
– Sumit, Commented Aug 6, 2018 at 11:27

Ramanathan Ganesan · Accepted Answer · 2018-08-06 06:39:54Z

1

There is not TRACE log level in python unless you have created a custom handler by yourself

Below is the list of log levels

Please refer there https://docs.python.org/2/library/logging.html#levels

answered Aug 6, 2018 at 6:39

Ramanathan Ganesan

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1 Comment

Sumit Over a year ago

I have added custom log level Trace with LevelNum 5

Vinay Sajip · Accepted Answer · 2018-08-06 14:07:55Z

1

Your code does not run: for example, pasting it into a source file, it fails because f is undefined. Commenting out that line, I got it to run without any problems. Are you sure that log_setup() is being called before the code in xyz? My guess is that it isn't. Also, the line

root.handlers = []

shouldn't be there - you shouldn't do this, as handlers is an internal attribute and not meant for you to change directly. The line

logging.trace = trace

also looks wrong, as the logging module-level convenience functions don't take an initial object argument, and have a signature such as debug(msg, *args, **kwargs). Presumably you would want a module-level trace function to have an analogous signature.

answered Aug 6, 2018 at 14:07

Vinay Sajip

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1 Comment

Sumit Over a year ago

Script from where I was calling was having call as root = logging.getLogger("TEST"). I changed this command to root = logging.getLogger("TEST."+__name) and it worked. Not sure why

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