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logging.getLogger('name').setLevel() does not seem to work [duplicate]

The below code is copied from the documentation. I am supposed to be able to see all the info logs. But I don't. I am only able to see the warn and above even though I've set setLevel to INFO.
Why is this happening? foo.py:
import logging
logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)
logger.debug('debug message')
logger.info('info message')
logger.warn('warn message')
logger.error('error message')
logger.critical('critical message')
Output:
workingDirectory$ python foo.py
warn message
error message
critical message
Where did the info and debug messages go??

Replace the line
logger.setLevel(logging.DEBUG)
with
logging.basicConfig(level=logging.DEBUG, format='%(message)s')
and it should work as expected. If you don't configure logging with any handlers (as in your post - you only configure a level for your logger, but no handlers anywhere), you'll get an internal handler "of last resort" which is set to output just the message (with no other formatting) at the WARNING level.

Try running logging.basicConfig() in there. Of note, I see you mention INFO, but use DEBUG. As written, it should show all five messages. Swap out DEBUG with INFO, and you should see four messages.
import logging
logging.basicConfig()
logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)
logger.debug('debug message')
logger.info('info message')
logger.warn('warn message')
logger.error('error message')
logger.critical('critical message')
edit: Do you have logging set up elsewhere in your code already? Can't reproduce the exact behavior you note with the specific code provided.

As pointed by some users, using:
logging.basicConfig(level=logging.DEBUG, format='%(message)s')
like written in the accepted answer is not a good option because it sets the log level for the root logger, so it may lead to unexpected behaviours (eg. third party libraries may start to log debug messages if you set loglevel=logging.DEBUG)
In my opinion the best solution is to set log level just for your logger, like this:
import logging
logger = logging.getLogger('MyLogger')
handler = logging.StreamHandler()
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
handler.setFormatter(formatter)
logger.addHandler(handler)
logger.setLevel(logging.DEBUG)
Not really intuitive solution, but is necessary if you want to set log level only for 'MyLogger' and leave the root logger untouched.
So, why is logging.basicConfig(level=logging.DEBUG, format='%(message)s') setting the log level globally?
Well, actually it doesn't. As said, it's just changing the configuration of the root logger and, as described in the python documentation:
Loggers should NEVER be instantiated directly, but always through the
module-level function logging.getLogger(name). Multiple calls to
getLogger() with the same name will always return a reference to the
same Logger object.
So, logging.basicConfig is creating a StreamHandler with a default Formatter and adding it to the root logger.
The point is that if any other library is using the "root logger", you're going to set that log level for that library too so it can happen that you start to see debug logs from third party libraries.
This is why I think it's better to create your own logger and set your own formatters and handlers, so you can leave the root logger untouched.

This is technically also an "answer", because it can "solve" the problem. BUT I definitely DO NOT like it. It is not intuitive, and I lost 2+ hours over it.
Before:
import logging
logger = logging.getLogger('foo')
logger.setLevel(logging.INFO)
logger.info('You can not see me')
# Or you can just use the following one-liner in command line.
# $ python -c "import logging; logger = logging.getLogger('foo'); logger.setLevel(logging.INFO); logger.info('You can not see me')"
After:
import logging
logging.debug('invisible magic') # <-- magic
logger = logging.getLogger('foo')
logger.setLevel(logging.INFO)
logger.info('But now you can see me')
# Or you can just use the following one-liner in command line.
$ python -c "import logging; logging.debug('invisible magic'); logger = logging.getLogger('foo'); logger.setLevel(logging.INFO); logger.info('But now you see me')"
PS: Comparing it to the current chosen answer, and #Vinay-Sajip's explanation, I can kind of understand why. But still, I wish it was not working that way.

If you want this to work WITHOUT basicConfig, you have to first set up the lowest possible level you'll log onto the logger. Since the logger sets a minimum threshold, handlers which have a lower threshold but belong to the same logger won't get those lower threshold messages since they're ignored by the logger in the first place. Intuitive, but not obvious.
We start by doing this:
lgr = logging.getLogger(name)
lgr.setLevel(logging.DEBUG)
Then, set up the handlers with the different levels you need, in my case I want DEBUG logging on stdout and INFO logging to a rotating file, so I do the following:
rot_hndlr = RotatingFileHandler('filename.log',
maxBytes=log_size,
backupCount=3)
rot_hndlr.setFormatter(formatter)
rot_hndlr.setLevel(logging.INFO)
lgr.addHandler(rot_hndlr)
stream_hndlr = logging.StreamHandler()
stream_hndlr.setFormatter(stream_formatter)
lgr.addHandler(stream_hndlr)
Then, to test, I do this:
lgr.debug("Hello")
lgr.info("There")
My stdout (console) will look like this:
Hello
There
and my filename.log file will look like this:
There

In short, change the level in logging.basicConfig will influence the global settings.
You should better set level for each logger and the specific handler in the logger.
The following is an example that displays all levels on the console and only records messages >= errors in log_file.log. Notice the level for each handler is different.
import logging
# Define logger
logger = logging.getLogger('test')
# Set level for logger
logger.setLevel(logging.DEBUG)
# Define the handler and formatter for console logging
consoleHandler = logging.StreamHandler() # Define StreamHandler
consoleHandler.setLevel(logging.DEBUG) # Set level
concolsFormatter = logging.Formatter('%(name)s - %(levelname)s - %(message)s') # Define formatter
consoleHandler.setFormatter(concolsFormatter) # Set formatter
logger.addHandler(consoleHandler) # Add handler to logger
# Define the handler and formatter for file logging
log_file = 'log_file'
fileHandler = logging.FileHandler(f'{log_file}.log') # Define FileHandler
fileHandler.setLevel(logging.ERROR) # Set level
fileFormatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s') # Define formatter
fileHandler.setFormatter(fileFormatter) # Set formatter
logger.addHandler(fileHandler) # Add handler to logger
# Test
logger.debug('This is a debug')
logger.info('This is an info')
logger.warning('This is a warning')
logger.error('This is an error')
logger.critical('This is a critical')
Console output:
# Test
test - DEBUG - This is a debug
test - INFO - This is an info
test - WARNING - This is a warning
test - ERROR - This is an error
test - CRITICAL - This is a critical
File log_file.log content:
2021-09-22 12:50:50,938 - test - ERROR - This is an error
2021-09-22 12:50:50,938 - test - CRITICAL - This is a critical
To review your logger's level:
logger.level
The result should be one of the following:
10 # DEBUG
20 # INFO
30 # WARNING
40 # ERROR
50 # CRITICAL
To review your handlers's levels:
logger.handlers
[<StreamHandler stderr (DEBUG)>,
<FileHandler ***/log_file.log (ERROR)>]

The accepted answer does not work for me on Win10, Python 3.7.2.
My solution:
logging.basicConfig(level=logging.DEBUG)
logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)
It's order sensitive.

You have to set the basicConfig of the root logger to DEBUG, then you can set the level of your individual loggers to more restrictive levels.
This is not what I expected. Here is what I had to do:
#!/usr/bin/env python3
import logging
# by default this is WARNING. Leaving it as WARNING here overrides
# whatever setLevel-ing you do later so it seems they are ignored.
logging.basicConfig(level=logging.DEBUG)
l = logging.getLogger(__name__)
l.setLevel(level=logging.INFO)
# if I hadn't called basicConfig with DEBUG level earlier,
# info messages would STILL not be shown despite calling
# setLevel above. However now debug messages will not be shown
# for l because setLevel set it to INFO
l.warning('A warning message will be displayed')
l.info('A friendly info message will be displayed')
l.debug('A friendly debug message will not be displayed')

Most of the answers that I've found for this issue uses the basicConfig of the root logger.
It's not helpful for those who intend to use multiple independent loggers that were not initialised with basicConfig. The use of basicConfig implies that the loglevels of ALL loggers will be changed. It also had the unfortunate side effect of generating duplicate logs.
So I tried over several days experimenting with different ways to manipulate the loglevels and came up with one that finally worked.
The trick was to not only change the log levels of all the handlers but also the all the handlers of the parent of the logger.
def setLevel(self, infoLevel):
# To dynamically reset the loglevel, you need to also change the parent levels as well as all handlers!
self.logger.parent.setLevel(infoLevel)
for handler in self.logger.parent.handlers:
handler.setLevel(infoLevel)
self.logger.setLevel(infoLevel)
for handler in self.logger.handlers:
handler.setLevel(infoLevel)
The inspiration came from the fact that the basicConfig changes the root logger settings, so I was trying to do the same without using basicConfig.
For those that are interested, I did a little Python project on Github that illustrates the different issues with setting loglevel of the logger (it works partially), proves the SLogger (Sample Logger) implementation works, and also illustrates the duplicate log issue with basicConfig when using multiple loggers not initialised with it.
https://github.com/FrancisChung/python-logging-playground
TLDR: If you're only interested in a working sample code for the logger, the implentation is listed below
import logging
CRITICAL = 50
FATAL = CRITICAL
ERROR = 40
WARNING = 30
WARN = WARNING
INFO = 20
DEBUG = 10
NOTSET = 0
class SLogger():
"""
SLogger : Sample Logger class using the standard Python logging Library
Parameters:
name : Name of the Logger
infoLevel : logging level of the Logger (e.g. logging.DEBUG/INFO/WARNING/ERROR)
"""
def __init__(self, name: str, infoLevel=logging.INFO):
try:
if name is None:
raise ValueError("Name argument not specified")
logformat = '%(asctime)s %(levelname)s [%(name)s %(funcName)s] %(message)s'
self.logformat = logformat
self.name = name.upper()
self.logger = logging.getLogger(self.name)
self.logger.setLevel(infoLevel)
self.add_consolehandler(infoLevel, logformat)
except Exception as e:
if self.logger:
self.logger.error(str(e))
def error(self, message):
self.logger.error(message)
def info(self, message):
self.logger.info(message)
def warning(self, message):
self.logger.warning(message)
def debug(self, message):
self.logger.debug(message)
def critical(self, message):
self.logger.critical(message)
def setLevel(self, infoLevel):
# To dynamically reset the loglevel, you need to also change the parent levels as well as all handlers!
self.logger.parent.setLevel(infoLevel)
for handler in self.logger.parent.handlers:
handler.setLevel(infoLevel)
self.logger.setLevel(infoLevel)
for handler in self.logger.handlers:
handler.setLevel(infoLevel)
return self.logger.level
def add_consolehandler(self, infoLevel=logging.INFO,
logformat='%(asctime)s %(levelname)s [%(name)s %(funcName)s] %(message)s'):
sh = logging.StreamHandler()
sh.setLevel(infoLevel)
formatter = logging.Formatter(logformat)
sh.setFormatter(formatter)
self.logger.addHandler(sh)

Create object the right way, e.g. inspired by Google:
import logging
formatter = logging.Formatter('%(asctime)s %(threadName)s: %(message)s')
log = logging.getLogger(__name__)
log.setLevel(logging.DEBUG)
handler = logging.StreamHandler()
handler.setFormatter(formatter)
log.addHandler(handler)
log.debug('debug message')
log.info('info message')
log.warn('warn message')
log.error('error message')
log.critical('critical message')
2022-11-22 23:17:59,342 MainThread: debug message
2022-11-22 23:17:59,342 MainThread: info message
2022-11-22 23:17:59,342 MainThread: warn message
2022-11-22 23:17:59,342 MainThread: error message
2022-11-22 23:17:59,342 MainThread: critical message

As pointed out by #ManuelFedele, logging.basicConfig is not a good solution.
#VinaySajip explained that the setLevel is ignored because the logger is using the internal handler "of last resort", whose level is set to WARNING.
This explanation was also helpful:
The Handler.setLevel() method, just as in logger objects, specifies the lowest severity that will be dispatched to the appropriate destination. Why are there two setLevel() methods? The level set in the logger determines which severity of messages it will pass to its handlers. The level set in each handler determines which messages that handler will send on.
So a good solution is to add a handler to the logger, with the appropriate level:
import logging
logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)
ch = logging.StreamHandler()
ch.setLevel(logging.DEBUG) # or whatever level should be displayed on the console
logger.addHandler(ch)
Output
>>> logger.debug('debug message')
debug message
>>> logger.info('info message')
info message
>>> logger.warn('warn message')
<stdin>:1: DeprecationWarning: The 'warn' method is deprecated, use 'warning' instead
warn message
>>> logger.error('error message')
error message
>>> logger.critical('critical message')
critical message

Multi module python logger using the name of the main module

I have multiple python modules that I'd like to use the same logger while preserving the call hierarchy in those logs. I'd also like to do this with a logger whose name is the name of the calling module (or calling module stack). I haven't been able to work out how to get the name of the calling module except with messing with the stack trace, but that doesn't feel very pythonic.
Is this possible?
main.py
import logging
from sub_module import sub_log
logger = logging.getLogger(__name__)
logger.info("main_module")
sub_log()
sub_module.py
import logging
def sub_log():
logger = logging.getLogger(???)
logger.info("sub_module")
Desired Output
TIME main INFO main_module
TIME main.sub_module INFO sub_module

To solve your problem pythonic use the Logger Formatter:
For reference check the
Logging Docs
main.py
import logging
from submodule import sub_log
from submodule2 import sub_log2
logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)
# create file handler which logs even debug messages
fh = logging.FileHandler('test.log')
fh.setLevel(logging.DEBUG)
# create formatter and add it to the handlers
formatter = logging.Formatter('%(asctime)s %(name)s.%(module)s - %(levelname)s - %(message)s')
fh.setFormatter(formatter)
# add the handlers to the logger
logger.addHandler(fh)
sub_log("test")
sub_log2("test")
submodule.py
import logging
import __main__
def sub_log(msg):
logger = logging.getLogger(__main__.__name__)
logger.info(msg)
I've created second submodule. ( same code other name)
My Results:
2018-10-16 20:41:23,860 __main__.submodule - INFO - test
2018-10-16 20:41:23,860 __main__.submodule2 - INFO - test
I hope this will help you :)

Set logging levels

I'm trying to use the standard library to debug my code:
This works fine:
import logging
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)
logger.info('message')
I can't make work the logger for the lower levels:
logging.basicConfig(level=logging.DEBUG)
logger = logging.getLogger(__name__)
logger.info('message')
logging.basicConfig(level=logging.DEBUG)
logger = logging.getLogger(__name__)
logger.debug('message')
I don't get any response for neither of those.

What Python version? That works for me in 3.4. But note that basicConfig() won't affect the root handler if it's already setup:
This function does nothing if the root logger already has handlers configured for it.
To set the level on root explicitly do logging.getLogger().setLevel(logging.DEBUG). But ensure you've called basicConfig() before hand so the root logger initially has some setup. I.e.:
import logging
logging.basicConfig()
logging.getLogger().setLevel(logging.DEBUG)
logging.getLogger('foo').debug('bah')
logging.getLogger().setLevel(logging.INFO)
logging.getLogger('foo').debug('bah')
Also note that "Loggers" and their "Handlers" both have distinct independent log levels. So if you've previously explicitly loaded some complex logger config in you Python script, and that has messed with the root logger's handler(s), then this can have an effect, and just changing the loggers log level with logging.getLogger().setLevel(..) may not work. This is because the attached handler may have a log level set independently. This is unlikely to be the case and not something you'd normally have to worry about.

I use the following setup for logging.
Yaml based config
Create a yaml file called logging.yml like this:
version: 1
formatters:
simple:
format: "%(name)s - %(lineno)d - %(message)s"
complex:
format: "%(asctime)s - %(name)s - %(lineno)d - %(message)s"
handlers:
console:
class: logging.StreamHandler
level: DEBUG
formatter: simple
file:
class: logging.handlers.TimedRotatingFileHandler
when: midnight
backupCount: 5
level: DEBUG
formatter: simple
filename : Thrift.log
loggers:
qsoWidget:
level: INFO
handlers: [console,file]
propagate: yes
__main__:
level: DEBUG
handlers: [console]
propagate: yes
Python - The main
The "main" module should look like this:
import logging.config
import logging
import yaml
with open('logging.yaml','rt') as f:
config=yaml.safe_load(f.read())
f.close()
logging.config.dictConfig(config)
logger=logging.getLogger(__name__)
logger.info("Contest is starting")
Sub Modules/Classes
These should start like this
import logging
class locator(object):
def __init__(self):
self.logger = logging.getLogger(__name__)
self.logger.debug('{} initialized')
Hope that helps you...

In my opinion, this is the best approach for the majority of cases.
Configuration via an INI file
Create a filename logging.ini in the project root directory as below:
[loggers]
keys=root
[logger_root]
level=DEBUG
handlers=screen,file
[formatters]
keys=simple,verbose
[formatter_simple]
format=%(asctime)s [%(levelname)s] %(name)s: %(message)s
[formatter_verbose]
format=[%(asctime)s] %(levelname)s [%(filename)s %(name)s %(funcName)s (%(lineno)d)]: %(message)s
[handlers]
keys=file,screen
[handler_file]
class=handlers.TimedRotatingFileHandler
interval=midnight
backupCount=5
formatter=verbose
level=WARNING
args=('debug.log',)
[handler_screen]
class=StreamHandler
formatter=simple
level=DEBUG
args=(sys.stdout,)
Then configure it as below:
import logging
from logging.config import fileConfig
fileConfig('logging.ini')
logger = logging.getLogger('dev')
name = "stackoverflow"
logger.info(f"Hello {name}!")
logger.critical('This message should go to the log file.')
logger.error('So should this.')
logger.warning('And this, too.')
logger.debug('Bye!')
If you run the script, the sysout will be:
2021-01-31 03:40:10,241 [INFO] dev: Hello stackoverflow!
2021-01-31 03:40:10,242 [CRITICAL] dev: This message should go to the log file.
2021-01-31 03:40:10,243 [ERROR] dev: So should this.
2021-01-31 03:40:10,243 [WARNING] dev: And this, too.
2021-01-31 03:40:10,243 [DEBUG] dev: Bye!
And debug.log file should contain:
[2021-01-31 03:40:10,242] CRITICAL [my_loger.py dev <module> (12)]: This message should go to the log file.
[2021-01-31 03:40:10,243] ERROR [my_loger.py dev <module> (13)]: So should this.
[2021-01-31 03:40:10,243] WARNING [my_loger.py dev <module> (14)]: And this, too.
All done.

I wanted to leave the default logger at warning level but have detailed lower-level loggers for my code. But it wouldn't show anything. Building on the other answer, it's critical to run logging.basicConfig() beforehand.
import logging
logging.basicConfig()
logging.getLogger('foo').setLevel(logging.INFO)
logging.getLogger('foo').info('info')
logging.getLogger('foo').debug('info')
logging.getLogger('foo').setLevel(logging.DEBUG)
logging.getLogger('foo').info('info')
logging.getLogger('foo').debug('debug')
Outputs expected
INFO:foo:info
INFO:foo:info
DEBUG:foo:debug
For a logging solution across modules, I did this
# cfg.py
import logging
logging.basicConfig()
logger = logging.getLogger('foo')
logger.setLevel(logging.INFO)
logger.info(f'active')
# main.py
import cfg
cfg.logger.info(f'main')

Python standard logging

I like using the python logging module because it standardizes my application and easier to get metrics. The problem I face is, for every application (or file.py) I am keep putting this on top of my code.
logger = logging.getLogger(__name__)
if not os.path.exists('log'):
os.makedirs('log')
logName=time.strftime("%Y%m%d.log")
hdlr = logging.FileHandler('log/%s'%(logName))
logger.setLevel(logging.INFO)
ch = logging.StreamHandler()
ch.setLevel(logging.DEBUG)
formatter = logging.Formatter('%(asctime)s - %(name)s - %(funcName)s %(levelname)s - %(message)s')
ch.setFormatter(formatter)
hdlr.setFormatter(formatter)
logger.addHandler(ch)
logger.addHandler(hdlr)
This is tedious and repetitive. Is there a better way to do this?
How do people log for a large application with multiple modules?

Take a look at logging.basicConfig().
If you wrap the basicConfig() in a function then you can just import your function and pass specific args (i.e. log filename, format, level, etc).
It will help to condense the code a bit and make it more extensible.
For example -
import logging
def test_logging(filename, format):
logging.basicConfig(filename=filename, format=format, level=logging.DEBUG)
# test
logging.info('Info test...')
logging.debug('Debug test...')
Then just import the test_logging() function into other programs.
Hope that this helps.

Read Using logging in multiple modules from Logging Cookbook.
What you need to do is to use getLogger() function to get a logger with a pre-defined settings.
import logging
logger = logging.getLogger('some_logger')
You set those settings just once at application startup time.

Get Output From the logging Module in IPython Notebook

When I running the following inside IPython Notebook I don't see any output:
import logging
logging.basicConfig(level=logging.DEBUG)
logging.debug("test")
Anyone know how to make it so I can see the "test" message inside the notebook?

Try following:
import logging
logger = logging.getLogger()
logger.setLevel(logging.DEBUG)
logging.debug("test")
According to logging.basicConfig:
Does basic configuration for the logging system by creating a
StreamHandler with a default Formatter and adding it to the root
logger. The functions debug(), info(), warning(), error() and
critical() will call basicConfig() automatically if no handlers are
defined for the root logger.
This function does nothing if the root logger already has handlers
configured for it.
It seems like ipython notebook call basicConfig (or set handler) somewhere.

If you still want to use basicConfig, reload the logging module like this
from importlib import reload # Not needed in Python 2
import logging
reload(logging)
logging.basicConfig(format='%(asctime)s %(levelname)s:%(message)s', level=logging.DEBUG, datefmt='%I:%M:%S')

My understanding is that the IPython session starts up logging so basicConfig doesn't work. Here is the setup that works for me (I wish this was not so gross looking since I want to use it for almost all my notebooks):
import logging
logger = logging.getLogger()
fhandler = logging.FileHandler(filename='mylog.log', mode='a')
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
fhandler.setFormatter(formatter)
logger.addHandler(fhandler)
logger.setLevel(logging.DEBUG)
Now when I run:
logging.error('hello!')
logging.debug('This is a debug message')
logging.info('this is an info message')
logging.warning('tbllalfhldfhd, warning.')
I get a "mylog.log" file in the same directory as my notebook that contains:
2015-01-28 09:49:25,026 - root - ERROR - hello!
2015-01-28 09:49:25,028 - root - DEBUG - This is a debug message
2015-01-28 09:49:25,029 - root - INFO - this is an info message
2015-01-28 09:49:25,032 - root - WARNING - tbllalfhldfhd, warning.
Note that if you rerun this without restarting the IPython session it will write duplicate entries to the file since there would now be two file handlers defined

Bear in mind that stderr is the default stream for the logging module, so in IPython and Jupyter notebooks you might not see anything unless you configure the stream to stdout:
import logging
import sys
logging.basicConfig(format='%(asctime)s | %(levelname)s : %(message)s',
level=logging.INFO, stream=sys.stdout)
logging.info('Hello world!')

What worked for me now (Jupyter, notebook server is: 5.4.1, IPython 7.0.1)
import logging
logging.basicConfig()
logger = logging.getLogger('Something')
logger.setLevel(logging.DEBUG)
Now I can use logger to print info, otherwise I would see only message from the default level (logging.WARNING) or above.

You can configure logging by running %config Application.log_level="INFO"
For more information, see IPython kernel options

I wanted a simple and straightforward answer to this, with nicely styled output so here's my recommendation
import sys
import logging
logging.basicConfig(
format='%(asctime)s [%(levelname)s] %(name)s - %(message)s',
level=logging.INFO,
datefmt='%Y-%m-%d %H:%M:%S',
stream=sys.stdout,
)
log = logging.getLogger('notebook')
Then you can use log.info() or any of the other logging levels anywhere in your notebook with output that looks like this
2020-10-28 17:07:08 [INFO] notebook - Hello world
2020-10-28 17:12:22 [INFO] notebook - More info here
2020-10-28 17:12:22 [INFO] notebook - And some more

As of logging version 3.8 a force parameter has been added that removes any existing handlers, which allows basicConfig to work. This worked on IPython version 7.29.0 and Jupyter Lab version 3.2.1.
import logging
logging.basicConfig(level=logging.DEBUG,
force = True)
logging.debug("test")

I setup a logger for both file and I wanted it to show up on the notebook. Turns out adding a filehandler clears out the default stream handlder.
logger = logging.getLogger()
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
# Setup file handler
fhandler = logging.FileHandler('my.log')
fhandler.setLevel(logging.DEBUG)
fhandler.setFormatter(formatter)
# Configure stream handler for the cells
chandler = logging.StreamHandler()
chandler.setLevel(logging.DEBUG)
chandler.setFormatter(formatter)
# Add both handlers
logger.addHandler(fhandler)
logger.addHandler(chandler)
logger.setLevel(logging.DEBUG)
# Show the handlers
logger.handlers
# Log Something
logger.info("Test info")
logger.debug("Test debug")
logger.error("Test error")

setup
import logging
# make a handler
handler = logging.StreamHandler()
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
handler.setFormatter(formatter)
# add it to the root logger
logging.getLogger().addHandler(handler)
log from your own logger
# make a logger for this notebook, set verbosity
logger = logging.getLogger(__name__)
logger.setLevel('DEBUG')
# send messages
logger.debug("debug message")
logger.info("so much info")
logger.warning("you've veen warned!")
logger.error("bad news")
logger.critical("really bad news")
2021-09-02 18:18:27,397 - __main__ - DEBUG - debug message
2021-09-02 18:18:27,397 - __main__ - INFO - so much info
2021-09-02 18:18:27,398 - __main__ - WARNING - you've veen warned!
2021-09-02 18:18:27,398 - __main__ - ERROR - bad news
2021-09-02 18:18:27,399 - __main__ - CRITICAL - really bad news
capture logging from other libraries
logging.getLogger('google').setLevel('DEBUG')
from google.cloud import storage
client = storage.Client()
2021-09-02 18:18:27,415 - google.auth._default - DEBUG - Checking None for explicit credentials as part of auth process...
2021-09-02 18:18:27,416 - google.auth._default - DEBUG - Checking Cloud SDK credentials as part of auth process...
2021-09-02 18:18:27,416 - google.auth._default - DEBUG - Cloud SDK credentials not found on disk; not using them
...