How to add logging to any Python script?

For basic logging:

import logging

logging.basicConfig(level=logging.INFO, format='%(asctime)s - %(levelname)s - %(message)s')

def my_function():
    logging.info("Start of my_function")
    # Your code
    logging.debug("Debugging intermediate information")
    try:
        result = 1 / 0
    except ZeroDivisionError:
        logging.error("Division by zero error")
    logging.info("End of my_function")

my_function()

For more flexible configuration, you can use a configuration file or dictionary:

import logging
import logging.config

# Example configuration in a dictionary
log_config = {
    'version': 1,
    'formatters': {
        'simpleFormatter': {
            'format': '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
        },
    },
    'handlers': {
        'consoleHandler': {
            'class': 'logging.StreamHandler',
            'formatter': 'simpleFormatter',
            'level': 'INFO'
        },
        'fileHandler': {
            'class': 'logging.FileHandler',
            'formatter': 'simpleFormatter',
            'level': 'DEBUG',
            'filename': 'app.log'
        }
    },
    'loggers': {
        'myApp': {
            'handlers': ['consoleHandler', 'fileHandler'],
            'level': 'DEBUG'
            'propagate': False
        }
    },
    'root': {
        'handlers': ['consoleHandler'],
        'level': 'INFO'
    }
}

logging.config.dictConfig(log_config)
logger = logging.getLogger('myApp')

def another_function():
    logger.info("Executing another_function")
    logger.debug("Execution details")

another_function()

Key elements:

• logging.basicConfig(): The simplest way to configure the root logger.
• logging.getLogger(name): Gets an instance of a logger. Using names allows creating a hierarchy of loggers for modules or applications.
• Logging levels:
  • DEBUG: Detailed information useful for debugging.
  • INFO: General information about execution progress.
  • WARNING: Warning about potential issues.
  • ERROR: An error that does not stop program execution.
  • CRITICAL: Critical error after which the program may terminate.
• Handlers: Define where to send log messages (console, file, network, etc.).
• Formatters: Define the output format of log messages.