How to add custom parameter into Python logging formatter?

Question

I\'m using standard Python logging module with Flask framework. I want to write logs to file with the all records of users actions with custom parameter - %(username)s to loggin

Answer 1

u can do it with logging.LoggerAdapter

myLogger = logging.LoggerAdapter(logging.getLogger("my-logger"), {"username" : get_user_name()})

Here is the complete solution for your program. I use a dict to build my configuration. It is better, if you have more logger

    def get_user_name():
        return session.get("username", "")

    LOGGING = {
        'version': 1,
        'disable_existing_loggers': True,
        'formatters': {
            'my_format': {
                'format': '%(username)s - %(asctime)s %(levelname)-10s %(message)s  [in %(pathname)s:%(lineno)d]'
            },
        },
        'handlers': {
            'my_handler': {
                'level': 'DEBUG',
                'class': 'logging.handlersRotatingFileHandler',
                'filename': fname,
                'maxBytes': 1 * 1024 * 1024,
                'backupCount': 5,
            },
        },
        'loggers': {
            'my_logger': {
                'handlers': ['my_handler'],
                'propagate': True,
                'level': 'DEBUG',
            },
        } }

logging.config.dictConfig(LOGGING) 
logging.LoggerAdapter(logging.getLogger('my_logger'),
                                           {"username" : get_user_name()})