Logging to Both File and Stdout in Python with the Logging Module

When utilizing the Python logging module, it's desirable to have log messages output not only to the specified log file but also to stdout for immediate visibility. To achieve this, the logging module provides a straightforward solution.

The logging configuration relies on handlers to direct output. By adding a logging.StreamHandler() instance to the root logger, it's possible to send messages to stdout in addition to their intended destinations.

An example of configuring a stream handler for stdout output:

import logging
import sys

# Get the root logger
root = logging.getLogger()

# Set the root logger level to DEBUG
root.setLevel(logging.DEBUG)

# Create a stream handler and set its level to DEBUG
handler = logging.StreamHandler(sys.stdout)
handler.setLevel(logging.DEBUG)

# Create a formatter to format the log messages
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
handler.setFormatter(formatter)

# Add the handler to the root logger
root.addHandler(handler)

By implementing this configuration, it becomes unnecessary to duplicate log messages using both logger methods and stdout print statements. Loggers such as mylogger.critical("something failed") will output to both the designated log file and stdout, providing immediate visibility while maintaining proper logging practices.