Log levels

Learn debug, info, warning, error, critical levels.

Log levels

Logging uses one of five levels: debug (10), info (20), warning (30), error (40), critical (50). The logger's level decides which messages are written.

logger.debug("ayıklama")     # 10
logger.info("bilgi")        # 20
logger.warning("uyarı")     # 30
logger.error("hata")        # 40
logger.critical("kritik")   # 50

Low-level messages (debug, info) are rarely used in production; high-level ones (error, critical) are always written.

Order and priority

Each level has a numeric value: DEBUG=10, INFO=20, WARNING=30, ERROR=40, CRITICAL=50. The logger writes only messages whose level is equal to or higher than its own.

logger.setLevel(logging.WARNING)
logger.debug("invisible")   # skipped
logger.warning("visible")   # written

This is used to silence low-level messages in production; during debugging you lower the level to DEBUG.

Exercise Print level values

Start with import logging. Print the numeric values of the first three levels with print(logging.DEBUG), print(logging.INFO) and print(logging.WARNING).

Show example solution

import logging

print(logging.DEBUG)
print(logging.INFO)
print(logging.WARNING)

Test yourself

Complete the info call

logger.____("bilgi")

Show answer

logger.info("bilgi")

What is the numeric value of logging.WARNING?
- 30
- 20
- 10
- 50
Show answer

30 — answer: 30. DEBUG is 10, INFO is 20, ERROR is 40, CRITICAL is 50.
Match the log levels concepts

debug

Lowest level
info

Info level
warning

Warning level
critical

Highest level

Next lesson: basicConfig

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