Making Python loggers output all messages to stdout in addition to log file

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Is there a way to make Python logging using the logging module automatically output things to stdout in addition to the log file where they are supposed to go? For example, I'd like all calls to logger.warning, logger.critical, logger.error to go to their intended places but in addition always be copied to stdout. This is to avoid duplicating messages like:

mylogger.critical("something failed")
print "something failed"

All logging output is handled by the handlers; just add a logging.StreamHandler() to the root logger.

Here's an example configuring a stream handler (using stdout instead of the default stderr) and adding it to the root logger:

import logging
import sys

root = logging.getLogger()
root.setLevel(logging.DEBUG)

handler = logging.StreamHandler(sys.stdout)
handler.setLevel(logging.DEBUG)
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
handler.setFormatter(formatter)
root.addHandler(handler)

Logging HOWTO, 1 Answer. For making Python loggers output all messages to stdout in addition to the log file you can use the following method which is using logging and sys module to : One thing to note that all the logging output is handled by the handlers, you just need to add logging. For making Python loggers output all messages to stdout in addition to the log file you can use the following method which is using logging and sys module to : import logging. import sys. logging.basicConfig(stream=sys.stdout, level=logging.DEBUG)

The simplest way to log to stdout:

import logging
import sys
logging.basicConfig(stream=sys.stdout, level=logging.DEBUG)

15.6. logging — Logging facility for Python, Display console output for ordinary usage of a command line script or program DEBUG) logging.debug('This message should go to the log file') to a log file, all log messages of error or higher to stdout, and all messages of critical to an Creating loggers, handlers, and formatters explicitly using Python code that calls​  February 20, 2020 Python Leave a comment. Questions: During a presentation yesterday I had a colleague run one of my scripts on a fresh installation of Python 3.8.1. It was able to create and write to a csv file in his folder (proof that the

It's possible using multiple handlers.

import logging
import auxiliary_module

# create logger with 'spam_application'
log = logging.getLogger('spam_application')
log.setLevel(logging.DEBUG)

# create formatter and add it to the handlers
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')

# create file handler which logs even debug messages
fh = logging.FileHandler('spam.log')
fh.setLevel(logging.DEBUG)
fh.setFormatter(formatter)
log.addHandler(fh)

# create console handler with a higher log level
ch = logging.StreamHandler()
ch.setLevel(logging.ERROR)
ch.setFormatter(formatter)
log.addHandler(ch)

log.info('creating an instance of auxiliary_module.Auxiliary')
a = auxiliary_module.Auxiliary()
log.info('created an instance of auxiliary_module.Auxiliary')

log.info('calling auxiliary_module.Auxiliary.do_something')
a.do_something()
log.info('finished auxiliary_module.Auxiliary.do_something')

log.info('calling auxiliary_module.some_function()')
auxiliary_module.some_function()
log.info('done with auxiliary_module.some_function()')

# remember to close the handlers
for handler in log.handlers:
    handler.close()
    log.removeFilter(handler)

Please see: https://docs.python.org/2/howto/logging-cookbook.html

Logging Cookbook, DEBUG) logging.debug('This message should go to the log file') It is sufficient to configure handlers for a top-level logger and create child loggers as needed. to a log file, all log messages of error or higher to stdout, and all messages of Running this module from the command line produces the following output:. Is there a way to overwrite log files in python 2.x. Specifies the mode to open the file, Making Python loggers output all messages to stdout in addition to

You could create two handlers for file and stdout and then create one logger with handlers argument to basicConfig. It could be useful if you have the same log_level and format output for both handlers:

import logging
import sys

file_handler = logging.FileHandler(filename='tmp.log')
stdout_handler = logging.StreamHandler(sys.stdout)
handlers = [file_handler, stdout_handler]

logging.basicConfig(
    level=logging.DEBUG, 
    format='[%(asctime)s] {%(filename)s:%(lineno)d} %(levelname)s - %(message)s',
    handlers=handlers
)

logger = logging.getLogger('LOGGER_NAME')

Python Logging Basics - The Ultimate Guide To Logging, DEBUG) # create file handler which logs even debug messages fh = logging. This shows the logging output interspersed as one might expect. All that changed was the addition and configuration of a new handler named fh. STDOUT) # wait for the program to finish p.communicate() def configure_logging​(): h  February 24, 2020 Python Leave a comment. Questions: I have some PDF files that I am (mostly) able to convert to text using the Nitro PDF tool. When I attempt to convert the same PDFs using the code posted here, I get output suggesting that t

The simplest way to log to file and to stderr:

import logging

logging.basicConfig(filename="logfile.txt")
stderrLogger=logging.StreamHandler()
stderrLogger.setFormatter(logging.Formatter(logging.BASIC_FORMAT))
logging.getLogger().addHandler(stderrLogger)

The Python logging module: How logging to file works, Python comes with a logging module in the standard library that provides a The rest of this article will focus on best practices instead of all the possible have is to make it easy for the application to route their log messages. Also if you use centralized logging, having to deal with additional log files is an added concern. 15.6.1.1. Simple examples¶. Most applications are probably going to want to log to a file, so let’s start with that case. Using the basicConfig() function, we can set up the default handler so that debug messages are written to a file (in the example, we assume that you have the appropriate permissions to create a file called example.log in the current directory):

Logging, You can use the Python logging module to display information logging from different servers, this Python logging module can make the work Some developers use the print output to check their script for errors. Debug includes all other levels and therefore displays all messages up to the critical error. Making Python loggers output all messages to stdout in addition to log file (4) All logging output is handled by the handlers; just add a logging.StreamHandler() to the root logger. Here's an example configuring a stream handler (using stdout instead of the default stderr ) and adding it to the root logger:

How to print logging messages to both stdout and to a file in Python, The logging module has been a part of Python's Standard Library since version 2.3. provides an approach to logging nearly as simple as using a simple print statement. The log record, which is created with every logging event, contains readily Pro: in addition to updating while running, it is possible to load from a file  This is the "Iris" dataset. Originally published at UCI Machine Learning Repository: Iris Data Set, this small dataset from 1936 is often used for testing out machine learning algorithms and visualizations (for example, Scatter Plot).

Python logging tutorial, DEBUG to capture all messages with a severity greater than or equal to debug messages. Call logging.FileHandler(file) to create a handler for the output file file . Handlers send the log records (created by loggers) to the appropriate destination. Filters provide a finer grained facility for determining which log records to output. Formatters specify the layout of log records in the final output. Log event information is passed between loggers, handlers, filters and formatters in a LogRecord instance.

Comments
  • Please check this answer stackoverflow.com/questions/9321741/…
  • That's fine but if it's already redirected to a file how can I have it be printed to stdout in addition?
  • @user248237: By adding a new handler as illustrated. New handlers do not replace the existing handlers, they also get to process the log entries.
  • @MartijnPieters is there a way to add a string to every log statement printed out?
  • @PrakharMohanSrivastava I'd guess you can just add it to the string passed into logging.Formatter.
  • @himanshu219: the use case is that as soon as you start adding multiple handlers, you usually want to differentiate. DEBUG to the console, WARNING and up to a file, etc.
  • Hm, but this isn't logged to a file, right? The question was how to do logging to file and to console.
  • Ref link: Python3 Docs: Logging.basicConfig
  • In Python 3 at least, it looks like omitting stream=sys.stdout still works for logging to the console for me.
  • @TaylorEdmiston Yeah, but it's the stderr stream AFAIK. Try redirecting the output from the shell.
  • OK. This doesn't answer both: logging to file and to console, but it was nice to find what I needed in 3 lines or less.
  • Wonderful answer, albeit a bit messy. Love how you show how to use different levels and formats for streams and files. +1, but +2 in spirit.
  • For me this did not work without the sys.stdout parameter in ch = logging.StreamHandler()
  • This works for me with python 3 but not with 2.7. I know python 2 is soon in end of life, but I'm curious why...