Logging — Better Than print()

The logging module provides proper logging with levels, formatting, and output control.

Basic setup:

import logging

logging.basicConfig(
    level=logging.DEBUG,
    format="%(asctime)s %(levelname)s %(message)s"
)

logging.debug("Debug info")      # development detail
logging.info("App started")      # general info
logging.warning("Low disk space") # unexpected but OK
logging.error("Database error")  # serious problem
logging.critical("System crash") # fatal

Log levels (lowest to highest): DEBUG < INFO < WARNING < ERROR < CRITICAL

Logging to file:

logging.basicConfig(
    filename="app.log",
    level=logging.INFO,
    format="%(asctime)s %(levelname)s %(message)s"
)

Logger per module:

logger = logging.getLogger(__name__)
logger.info("This module started")

Why not print: Logging has levels (easily turn off debug in production), timestamps, source info, and can write to files, email, or services simultaneously.

Reference:

Wikipedia: Logging

https://en.wikipedia.org/wiki/Logging_(software)