log_example.py

# This is a logging configuration that will log to both the console and a file (based on 'handlers').
# The 'loggers' section describes what levels get output:
#    textloading module will only output DEBUG messages (and above)
#    requests module will only output WARN messages (and above)
#    everything else will output INFO messages (and above)

LOGGING = {
    'version': 1,
    'disable_existing_loggers': True,
    'loggers': {
        '': {
            'handlers': ['file', 'console'],
            'propagate': True,
            'level': 'INFO'
        },
        'textloading': {
            'level': 'DEBUG'
        },
        'requests': {
            'level': 'WARN'
        },
    },
    'formatters': {
        'standard': {
            'datefmt': '%Y-%m-%d %H:%M:%S',
            'format': '%(asctime)s = %(name)s = %(levelname)s = %(message)s'
        }
    },
    'handlers': {
        'console': {
            'formatter': 'standard',
            'class': 'logging.StreamHandler'
        },
        'file': {
            'filename': 'log_filename.log',
            'formatter': 'standard',
            'mode': 'w',
            'class': 'logging.FileHandler'
        }
    }
}




# Run this ONE TIME to configure logging:

from logging.config import dictConfig

dictConfig(LOGGING)




# In any module, you can do the following:

import logging

logger = logging.getLogger(__name__) # to use current module name, OR:
logger = logging.getLogger('module.name') # to use a different module name




# Then once you do that, you can spit out your logging messages at any level:

logger.debug('I am a debug message.')
logger.error('This is an error message.')




# And there's a special case for exception handling. This will log at ERROR level, but also,
# the exception info is passed along with the log message, so you can use %(exc_info)s
# in the log formatter in the logging dict

try:
    # do stuff that causes error
except Exception:
    logger.exception('I am an error message')





# Quick exmaple. Let's say I have the following in textloading/taxiways/extract.py:

import logging

logger = logging.getLogger(__name__)

logger.info('starting process')

# That would send out a log message that looks like this:

# 2016-03-15 12:12:52 = textloading.taxiways.extract = INFO = starting process