Logger and Handler in Python Logging

🛠 Tools and Programming 💻Programming
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Short Definition:
A Handler in Python’s logging framework is an object responsible for dispatching log records (LogRecord) to their destination—such as files, terminals, emails, or network locations. Loggers generate the log records; Handlers receive these records and write or send them elsewhere. :white_check_mark:

Key Points

  • Separation of Responsibilities: Loggers produce messages; Handlers are responsible for sending/storing them.
  • Common Types: FileHandler, StreamHandler, RotatingFileHandler, SMTPHandler, etc.
  • Configurable: Each Handler has its own level (for filtering logs) and formatter (for formatting the log text).
  • Multiple Handlers: You can attach multiple Handlers to a single Logger, enabling the same log message to be sent to multiple destinations. Be cautious about duplicate output or resource leaks (e.g., unclosed file handles).

Example

import logging

logger = logging.getLogger("multi_ocr_sdk")
fh = logging.FileHandler("/path/to/logfile.log")
fh.setLevel(logging.INFO)
fh.setFormatter(logging.Formatter("%(asctime)s %(levelname)s %(message)s"))
logger.addHandler(fh)

logger.info("This is a log message")

Tip: When replacing a log file, remember to first call close() and removeHandler() on the old file handler to avoid file descriptor leaks and ensure logs are written to the latest file. :sparkles: