Configuring Logger for Error Messages Only

To configure your logger to write only error messages to a dedicated log file, you need to set the appropriate log level and handler configuration. Here's how you can modify your logging setup:

Solution

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import logging

# Get the logger
logger = logging.getLogger('django')

# Create a file handler for error logs only
error_handler = logging.FileHandler('error.log')
error_handler.setLevel(logging.ERROR)  # Only capture ERROR and above

# Create a formatter
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
error_handler.setFormatter(formatter)

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

# If you want to prevent the logger from propagating logs to the root logger
# (which might be capturing all levels)
logger.propagate = False

This configuration will:

1. Create a file handler that writes to 'error.log'
2. Set the handler's level to ERROR, so it only captures ERROR, CRITICAL, and FATAL messages
3. Format the log messages with timestamp, logger name, level, and message
4. Add the handler to your django logger
5. Optionally prevent log propagation to parent loggers

Handling print() Statements

Note that print() statements don't go through the logging system by default. If print statements are appearing in your log files, it's likely because:

1. Your application is redirecting stdout to the log file
2. You're using a WSGI/ASGI server that captures stdout and sends it to logs

To prevent print statements from appearing in logs, you should:

• Replace print() with appropriate logging calls (logger.debug(), logger.info(), etc.)
• Configure your web server to separate stdout from your error logs

Django-specific Configuration

If you're using Django, you might want to configure logging in your settings.py file:

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LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'handlers': {
        'error_file': {
            'level': 'ERROR',
            'class': 'logging.FileHandler',
            'filename': 'error.log',
            'formatter': 'verbose',
        },
    },
    'formatters': {
        'verbose': {
            'format': '{levelname} {asctime} {module} {message}',
            'style': '{',
        },
    },
    'loggers': {
        'django': {
            'handlers': ['error_file'],
            'level': 'ERROR',
            'propagate': False,
        },
    },
}

This will ensure that only ERROR and higher level messages from the 'django' logger are written to your error.log file.