Installlation

pip install loguru

Basic Usage

from loguru import logger

logger.trace("This is a trace level log")  # Most detailed information, typically used for debugging issues
logger.debug("This is a debug level log")  # Detailed information useful for debugging the program
logger.info("This is an info level log")  # General information confirming the program works as expected
logger.success("This is a success level log")  # Indicates a successful event (specific to loguru)
logger.warning("This is a warning level log")  # Indicates an unexpected situation that still runs normally
logger.error("This is an error level log")  # Indicates a serious problem causing a function failure
logger.critical("This is a critical level log")  # Severe error that may cause program termination

Logging Excpetion Stack Traces

logger.exception("This is an exception level log")
# logger.exception() should be used within an except block because it needs the current exception context
# Compared to logger.error(), it automatically records the exception stack trace

Logger Handler

# By default, the logger has one handler that outputs logs to the console

# Add a handler; the same logger can have multiple handlers that work simultaneously
handler_id = logger.add(sys.stderr)  # sys.stderr is standard error output
# Remove a handler
logger.remove(handler_id)
# Remove all handlers
logger.remove()
# Add a file logging handler
logger.add("test.log")
# Additional parameters for add method
logger.add(
    "test.log",
    rotation="1 MB",  # Creates a new file when the log reaches 1MB, generating a new name like test.log.1
    compression="zip",  # Compresses the log files
    enqueue=True,  # Enables asynchronous queue to avoid blocking threads using the logger, improving concurrent write performance, recommended when using coroutines
    encoding="utf-8",  # Sets the encoding for the log file
    format="{time} {level} {message}",  # Sets the log format
    filter="my_module",  # Filters logs from specific modules, recording only logs from my_module module. More filtering options are available for flexible configuration.
    level="INFO",  # Sets the log level
)
# Other examples for rotation parameter:
# "12:00"  # Creates a new log file every day at noon
# "1 week"  # Creates a new log file every week

# Filename placeholders:
# "test_{time}.log", the logger replaces this with the current time when creating the file, e.g., test_2021-01-01.log

Logger.catch Decoraotr

@logger.catch
def my_function():
    pass


# Using this decorator, exceptions in the function are caught, not propagated upwards, and detailed stack traces are printed/logged

Notes

# The logger object can be used across multiple modules and threads, and it is thread-safe.
# If the file specified by the logger handler is deleted, the handler's file handle no longer points to a file. Even if a file with the same name is created, it cannot continue writing. This handler becomes useless but occupies memory and needs to be removed.