Where is a complete example of logging.config.dictConfig?

The accepted answer is nice! But what if one could begin with something less complex? The logging module is very powerful thing and the documentation is kind of a little bit overwhelming especially for novice. But for the beginning you don’t need to configure formatters and handlers. You can add it when you figure out what you want.

For example:

import logging.config

DEFAULT_LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'loggers': {
        '': {
            'level': 'INFO',
        },
        'another.module': {
            'level': 'DEBUG',
        },
    }
}

logging.config.dictConfig(DEFAULT_LOGGING)

logging.info('Hello, log')

I found Django v1.11.15 default config below, hope it helps

DEFAULT_LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'filters': {
        'require_debug_false': {
            '()': 'django.utils.log.RequireDebugFalse',
        },
        'require_debug_true': {
            '()': 'django.utils.log.RequireDebugTrue',
        },
    },
    'formatters': {
        'django.server': {
            '()': 'django.utils.log.ServerFormatter',
            'format': '[%(server_time)s] %(message)s',
        }
    },
    'handlers': {
        'console': {
            'level': 'INFO',
            'filters': ['require_debug_true'],
            'class': 'logging.StreamHandler',
        },
        'django.server': {
            'level': 'INFO',
            'class': 'logging.StreamHandler',
            'formatter': 'django.server',
        },
        'mail_admins': {
            'level': 'ERROR',
            'filters': ['require_debug_false'],
            'class': 'django.utils.log.AdminEmailHandler'
        }
    },
    'loggers': {
        'django': {
            'handlers': ['console', 'mail_admins'],
            'level': 'INFO',
        },
        'django.server': {
            'handlers': ['django.server'],
            'level': 'INFO',
            'propagate': False,
        },
    }
}

Example with Stream Handler, File Handler, Rotating File Handler and SMTP Handler

from logging.config import dictConfig

LOGGING_CONFIG = {
    'version': 1,
    'loggers': {
        '': {  # root logger
            'level': 'NOTSET',
            'handlers': ['debug_console_handler', 'info_rotating_file_handler', 'error_file_handler', 'critical_mail_handler'],
        },
        'my.package': { 
            'level': 'WARNING',
            'propagate': False,
            'handlers': ['info_rotating_file_handler', 'error_file_handler' ],
        },
    },
    'handlers': {
        'debug_console_handler': {
            'level': 'DEBUG',
            'formatter': 'info',
            'class': 'logging.StreamHandler',
            'stream': 'ext://sys.stdout',
        },
        'info_rotating_file_handler': {
            'level': 'INFO',
            'formatter': 'info',
            'class': 'logging.handlers.RotatingFileHandler',
            'filename': 'info.log',
            'mode': 'a',
            'maxBytes': 1048576,
            'backupCount': 10
        },
        'error_file_handler': {
            'level': 'WARNING',
            'formatter': 'error',
            'class': 'logging.FileHandler',
            'filename': 'error.log',
            'mode': 'a',
        },
        'critical_mail_handler': {
            'level': 'CRITICAL',
            'formatter': 'error',
            'class': 'logging.handlers.SMTPHandler',
            'mailhost' : 'localhost',
            'fromaddr': '[email protected]',
            'toaddrs': ['[email protected]', '[email protected]'],
            'subject': 'Critical error with application name'
        }
    },
    'formatters': {
        'info': {
            'format': '%(asctime)s-%(levelname)s-%(name)s::%(module)s|%(lineno)s:: %(message)s'
        },
        'error': {
            'format': '%(asctime)s-%(levelname)s-%(name)s-%(process)d::%(module)s|%(lineno)s:: %(message)s'
        },
    },

}

dictConfig(LOGGING_CONFIG)

There’s an updated example of declaring a logging.config.dictConfig() dictionary schema buried in the logging cookbook examples. Scroll up from that cookbook link to see a use of dictConfig().

Here’s an example use case for logging to both stdout and a "logs" subdirectory using a StreamHandler and RotatingFileHandler with customized format and datefmt.

1. Imports modules and establish a cross-platform absolute path to the "logs" subdirectory

   from os.path import abspath, dirname, join
   import logging
   from logging.config import dictConfig
   base_dir = abspath(dirname(__file__))
   logs_target = join(base_dir + "logs", "python_logs.log")
   

2. Establish the schema according to the dictionary schema documentation.

   logging_schema = {
       # Always 1. Schema versioning may be added in a future release of logging
       "version": 1,
       # "Name of formatter" : {Formatter Config Dict}
       "formatters": {
           # Formatter Name
           "standard": {
               # class is always "logging.Formatter"
               "class": "logging.Formatter",
               # Optional: logging output format
               "format": "%(asctime)st%(levelname)st%(filename)st%(message)s",
               # Optional: asctime format
               "datefmt": "%d %b %y %H:%M:%S"
           }
       },
       # Handlers use the formatter names declared above
       "handlers": {
           # Name of handler
           "console": {
               # The class of logger. A mixture of logging.config.dictConfig() and
               # logger class-specific keyword arguments (kwargs) are passed in here. 
               "class": "logging.StreamHandler",
               # This is the formatter name declared above
               "formatter": "standard",
               "level": "INFO",
               # The default is stderr
               "stream": "ext://sys.stdout"
           },
           # Same as the StreamHandler example above, but with different
           # handler-specific kwargs.
           "file": {  
               "class": "logging.handlers.RotatingFileHandler",
               "formatter": "standard",
               "level": "INFO",
               "filename": logs_target,
               "mode": "a",
               "encoding": "utf-8",
               "maxBytes": 500000,
               "backupCount": 4
           }
       },
       # Loggers use the handler names declared above
       "loggers" : {
           "__main__": {  # if __name__ == "__main__"
               # Use a list even if one handler is used
               "handlers": ["console", "file"],
               "level": "INFO",
               "propagate": False
           }
       },
       # Just a standalone kwarg for the root logger
       "root" : {
           "level": "INFO",
           "handlers": ["file"]
       }
   }
   

3. Configure logging with the dictionary schema

   dictConfig(logging_schema)
   

4. Try some test cases to see if everything is working properly

   if __name__ == "__main__":
       logging.info("testing an info log entry")
       logging.warning("testing a warning log entry")
   

[EDIT to answer @baxx’s question]

5. To reuse this setting across your code base, instantiate a logger in the script you call dictConfig() and then import that logger elsewhere

    # my_module/config/my_config.py
    dictConfig(logging_schema)
    my_logger = getLogger(__name__)
   

Then in another script

    from my_module.config.my_config import my_logger as logger
    logger.info("Hello world!")

One more thing in case it’s useful to start from the existing logger’s config, the current config dictionary is can be obtained via

import logging
logger = logging.getLogger()
current_config = logger.__dict__  # <-- yes, it's just the dict

print(current_config)  

It’ll be something like:

{'filters': [], 'name': 'root', 'level': 30, 'parent': None, 'propagate': True, 'handlers': [], 'disabled': False, '_cache': {}}

Then, if you just do

new_config=current_config

new_config['version']=1
new_config['name']='fubar'
new_config['level']=20
#  ...and whatever other changes you wish

logging.config.dictConfig(new_config)

You will then find:

print(logger.__dict__)

is what you’d hope for

{'filters': [], 'name': 'fubar', 'level': 20, 'parent': None, 'propagate': True, 'handlers': [], 'disabled': False, '_cache': {}, 'version': 1}