Gavin Wiggins

Delay Log File Creation

Published on March 27, 2025
Tagged with python

Use the delay argument for Python's log file handler to avoid creating unnecessary log files. This ensures that a log file is created only for the desired log levels.

The example below creates a logger with a file handler that only tracks critical events. However, the log file is created even if a non-critical event is logged. Consequently, an empty log file is created when messages are logged at a level that is lower than the set level.

# Log file is created even for non-critical log messages

import logging

logger = logging.getLogger(__name__)
logger.setLevel(logging.CRITICAL)

handler = logging.FileHandler("example.log")
logger.addHandler(handler)

logger.error("This is the error log message.")

Set the delay=True argument for the file handler to avoid creating an empty log file. This will ensure that the log file is only created when a critical-level log message occurs as shown in the example below.

# Log file is only created for critical log messages

import logging
import time

logger = logging.getLogger(__name__)
logger.setLevel(logging.CRITICAL)

handler = logging.FileHandler("example.log", delay=True)
logger.addHandler(handler)

# Create error-level log message but will not create a log file
logger.error("This is the error log message.")
print("Notice no log file has been created")
time.sleep(4)

# Create critical-level log message and will create a log file
logger.critical("This is the critical error log message.")

Delay Log File Creation

Further Reading