Adding File Handlers for Log Storage

In addition to logging to the console, you can also store log messages in files for later analysis or archiving. This is particularly useful for long-running applications or when you need to review historical logs.

Creating a File Handler

Import the FileHandler:

Python

import logging.handlers

Create a File Handler:

Python

file_handler = logging.handlers.RotatingFileHandler(‘app.log’, maxBytes=102400, backupCount=5)

This creates a file handler that writes logs to the app.log file. When the file size exceeds 100 KB (102400 bytes), a new file is created and the old file is renamed to app.log.1, app.log.2, etc., up to 5 backup files.

Set the Formatter:

Python

formatter = logging.Formatter(‘%(asctime)s – %(name)s – %(levelname)s – %(message)s’)
file_handler.setFormatter(formatter)

Add the Handler to the Logger:

Python

logger.addHandler(file_handler)

Using a Rotating File Handler

Rotating file handlers are useful for managing log file size and preventing them from becoming too large. You can configure the maxBytes and backupCount parameters to control the maximum file size and the number of backup files.

Using a TimedRotatingFileHandler

For rotating logs based on time intervals (e.g., daily, weekly, monthly), use the TimedRotatingFileHandler:

Python

file_handler = logging.handlers.TimedRotatingFileHandler('app.log', when='midnight', interval=1)