13.2. Logging Levels

  • Critical - Error, cannot continue

  • Error - Error, can continue

  • Warning - Warning, will do something important

  • Info - I will do something

  • Debug - This is how I am doing this

13.2.1. Default Level

Default level is WARNING, so all the information with level below will not be displayed.

>>> import logging
>>>
>>>
>>> logging.critical('Error, cannot continue')
>>> logging.error('Error, can continue')
>>> logging.warning('Information, warn about something')
>>> logging.info('Information, inform about something')
>>> logging.debug('Debug, show detailed debugging information')

13.2.2. Change Level

In logging you can set minimum level required. Setting it to DEBUG will show all the information above DEBUG level, which means everything.

>>> import logging
>>>
>>>
>>> logging.basicConfig(level='DEBUG')
>>>
>>> logging.critical('Error, cannot continue')
>>> logging.error('Error, can continue')
>>> logging.warning('Information, warn about something')
>>> logging.info('Information, inform about something')
>>> logging.debug('Debug, show detailed debugging information')

Setting it to ERROR will display only error and critical information.

>>> import logging
>>>
>>>
>>> logging.basicConfig(level='ERROR')
>>>
>>> logging.critical('Error, cannot continue')
>>> logging.error('Error, can continue')
>>> logging.warning('Information, warn about something')
>>> logging.info('Information, inform about something')
>>> logging.debug('Debug, show detailed debugging information')

You can also use logging.ERROR constant. Note, that similar constants exists for other levels too.

>>> import logging
>>>
>>>
>>> logging.basicConfig(level=logging.ERROR)
>>>
>>> logging.critical('Error, cannot continue')
>>> logging.error('Error, can continue')
>>> logging.warning('Information, warn about something')
>>> logging.info('Information, inform about something')
>>> logging.debug('Debug, show detailed debugging information')

13.2.3. Error vs. Critical

  • Critical - not working, and cannot continue (fatal)

  • Error - not working, but can continue (it is not fatal)

For example, if we have files:

>>> TEMPERATURE_DATA_FILES = [
...     '2000-01-01.csv',
...     '2000-01-02.csv',
...     '2000-01-03.csv',
...     '2000-01-04.csv',
...     '2000-01-05.csv',  # corrupted
...     '2000-01-06.csv',
...     '2000-01-07.csv',
...     # ...
...     '2000-01-30.csv',
...     '2000-01-31.csv',
... ]

>>> def mean_temperature_for_jan05():
...     logging.critical('File "2000-01-05.csv" is corrupted')

>>> def mean_temperature_for_month():
...     logging.error('File "2000-01-05.csv" is corrupted')

13.2.4. Use Case - 1

>>> import logging
>>> import sys
>>>
>>>
>>> match sys.argv[1]:
...     case '--error': logging.basicConfig(level='ERROR')
...     case '--warning': logging.basicConfig(level='WARNING')
...     case '--info': logging.basicConfig(level='INFO')
...     case '--debug': logging.basicConfig(level='DEBUG')
...     case _: logging.basicConfig(level='ERROR')
>>>
>>>
>>> logging.critical('Example message')
>>> logging.error('Example message')
>>> logging.warning('Example message')
>>> logging.info('Example message')
>>> logging.debug('Example message')