logging मॉड्यूल की मूल बातें

import logging

logging.basicConfig(level=logging.DEBUG)
logging.debug("debug message")
logging.info("info message")
logging.warning("warning message")
logging.error("error message")
logging.critical("critical message")

import logging
# Numeric values:
# DEBUG    = 10
# INFO     = 20
# WARNING  = 30
# ERROR    = 40
# CRITICAL = 50

logging.basicConfig(level=logging.WARNING)
logging.debug("hidden")   # not shown
logging.warning("shown")  # shown

import logging

logger = logging.getLogger(__name__)

def process(data):
    logger.info("Processing %d items", len(data))
    return [x * 2 for x in data]

import logging

logging.basicConfig(
    level=logging.DEBUG,
    format="%(asctime)s %(levelname)s %(name)s — %(message)s",
    datefmt="%Y-%m-%d %H:%M:%S",
)

import logging

fmt = "%(asctime)s | %(levelname)-8s | %(name)s:%(lineno)d | %(message)s"
logging.basicConfig(level=logging.DEBUG, format=fmt)
logging.info("Server started on port 8080")

import logging
logger = logging.getLogger(__name__)

try:
    1 / 0
except ZeroDivisionError:
    logger.exception("Division failed")
    # Logs message + traceback automatically

import logging
logger = logging.getLogger(__name__)

logging.basicConfig(
    format="%(asctime)s %(levelname)s [%(user)s] %(message)s"
)
logger.info("Login successful", extra={"user": "alice"})

import logging
logger = logging.getLogger(__name__)

# BAD (always builds the string):
logger.debug(f"Processing {len(data)} items")

# GOOD (only builds if DEBUG is enabled):
logger.debug("Processing %d items", len(data))

import logging

logging.disable(logging.CRITICAL)  # suppress everything
# All log calls now silently do nothing

logging.disable(logging.NOTSET)    # re-enable

import logging

parent = logging.getLogger("myapp")
child = logging.getLogger("myapp.database")

# child propagates to parent by default
child.warning("DB slow")  # also appears in myapp's handlers

import logging

root = logging.getLogger()  # root logger
root.setLevel(logging.DEBUG)

handler = logging.StreamHandler()
root.addHandler(handler)