18.9. Logging Use Cases

18.9.1. Use Case - 1

import logging
import os

logging.basicConfig(
    format='"{asctime}", "{levelname}", "{message}"',
    filename='...',
    style='{'
)

log = logging.getLogger(__name__)
level = os.getenv('LOG_LEVEL', 'INFO')
log.setLevel(level)


log.critical('Critical error... finishing')
log.error('Some problem but can continue')
log.warning('Warning, this is important')
log.info('Typical message')
log.debug('Debug message with extra information')


logging.getLogger('requests').setLevel('DEBUG')
logging.getLogger('_tmp').setLevel('ERROR')

18.9.2. Use Case - 2

from datetime import datetime
import logging

logging.basicConfig(
    level='DEBUG',
    datefmt='%Y-%m-%d %H:%M:%S',
    format='[{levelname}] {message}',
    style='{'
)


def timeit(func):
    def wrapper(*args, **kwargs):
        time_start = datetime.now()
        result = func(*args, **kwargs)
        time_end = datetime.now()
        time = time_end - time_start
        logging.debug(f'Time: {time}')
        return result
    return wrapper


def debug(func):
    def wrapper(*args, **kwargs):
        function = func.__name__
        logging.debug(f'Calling: {function=}, {args=}, {kwargs=}')
        result = func(*args, **kwargs)
        logging.debug(f'Result: {result}')
        return result
    return wrapper


@timeit
@debug
def add_numbers(a, b):
    return a + b


add_numbers(1, 2)
# [DEBUG] Calling: function='add_numbers', args=(1, 2), kwargs={}
# [DEBUG] Result: 3
# [DEBUG] Time: 0:00:00.000105

add_numbers(1, b=2)
# [DEBUG] Calling: function='add_numbers', args=(1,), kwargs={'b': 2}
# [DEBUG] Result: 3
# [DEBUG] Time: 0:00:00.000042

add_numbers(a=1, b=2)
# [DEBUG] Calling: function='add_numbers', args=(), kwargs={'a': 1, 'b': 2}
# [DEBUG] Result: 3
# [DEBUG] Time: 0:00:00.000040

18.9.3. Use Case - 3

✘

>>> from datetime import datetime
>>> from uuid import uuid1
>>> import logging
>>>
>>>
>>> logging.basicConfig(
...     level='WARNING',
...     datefmt='%Y-%m-%d %H:%M:%S',
...     format='[{levelname}] {message}',
...     style='{'
... )
>>>
>>>
>>> class MyError(Exception):
...     def __init__(self, *args, **kwargs):
...         self.name = self.__class__.__name__
...         self.reason = self.args[0]
...
...         # make a UUID based on the host ID and current time
...         self.uuid = str(uuid1())
...
...         # save when exception occurred
...         self.when = datetime.now()
...
...         # run normal processing of the exception
...         super().__init__(*args, **kwargs)
>>>
>>>
>>> def run():
...     raise MyError('Error, because it is not working')
>>>
>>>
>>> try:
...     run()
... except Exception as error:
...     name = self.name
...     reason = self.reason
...     when = error.when.strftime('%Y-%m-%d %H:%M:%S')
...     identifier = error.uuid
...
...     # you can write this error to the database
...     # or print it on the stderr
...     logging.error(f'Error happened: {name=}, {reason=}, {when=}, {identifier=}')
[ERROR] Error happened: name='MyError', reason='Error, because it is not working', when='1969-07-21 02:56:15', identifier='886a59c4-8431-11ec-95bc-acde48001122'