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

2.6K Asked by RutujaMishra in Python , Asked on Apr 7, 2021

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"

Answered by Rutuja Mishra

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)

Note

All the logging output is handled by the handlers, you just need to add logging.StreamHandler() to the logger which is root.

Below is an example for python logging stdout, using stdout instead of the default stderr and also 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)

Your Answer

Answer (1)

Ranjana

To configure Python's logging module to output all log messages to both the standard output (stdout) and a log file, you can set up multiple handlers. Here is a step-by-step guide on how to achieve this:

  Import the necessary modules:import logging

Create and configure the logger:

  logger = logging.getLogger('my_logger')logger.setLevel(logging.DEBUG)  # Set the logger level to DEBUG

Create handlers for both the file and stdout:

  # File handlerfile_handler = logging.FileHandler('logfile.log')file_handler.setLevel(logging.DEBUG)  # Set the level for the file handler# Stdout handlerconsole_handler = logging.StreamHandler()console_handler.setLevel(logging.DEBUG)  # Set the level for the console handler

Create a formatter and set it for both handlers:

  formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')file_handler.setFormatter(formatter)console_handler.setFormatter(formatter)

Add the handlers to the logger:

  logger.addHandler(file_handler)logger.addHandler(console_handler)

Example usage of the logger:

  logger.debug('This is a debug message')logger.info('This is an info message')logger.warning('This is a warning message')logger.error('This is an error message')logger.critical('This is a critical message')

Here's the complete example code:

  import logging# Create and configure the loggerlogger = logging.getLogger('my_logger')logger.setLevel(logging.DEBUG)# Create handlersfile_handler = logging.FileHandler('logfile.log')console_handler = logging.StreamHandler()# Set level for handlersfile_handler.setLevel(logging.DEBUG)console_handler.setLevel(logging.DEBUG)# Create a formatter and set it for the handlersformatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')file_handler.setFormatter(formatter)console_handler.setFormatter(formatter)# Add handlers to the loggerlogger.addHandler(file_handler)logger.addHandler(console_handler)# Example usage of the loggerlogger.debug('This is a debug message')logger.info('This is an info message')logger.warning('This is a warning message')logger.error('This is an error message')logger.critical('This is a critical message')

This setup ensures that all log messages are output to both the standard output and the log file. You can adjust the log levels and formats as needed for your specific use case.

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