Colab

setup

  1. import the logging module
  2. call .basicConfig()
  3. setup autoreload to help reloading .py files from disk
### useful: please run this
import logging
logging.basicConfig()

%load_ext autoreload
%autoreload 2

Basic

  1. import
  2. Create a new python file named ex1.py which should:
    1. Import the logging module
    2. create a logger instance named __name__
    3. Create a function called say_something() that logs a ‘warning’ message with the text: "This a warning message!".
  3. use the file
    1. import ex1
    2. call ex1.say_something()
%%file ex1.py

import logging
logger = logging.getLogger(__name__)

def say_something():
    logger.warning('this is a warning message')


Overwriting ex1.py

### useful: run your ex1.py
import ex1
ex1.say_something()

Log level

  1. Create a new python file named ‘ex2.py‘ which should:
    1. Import the logging module
    2. create a logger instance named __name__
    3. set the logger’s level to logging.DEBUG
    4. create a function called say_something() which logs an ‘info’ message with the text: “This an informative message!”.
  2. use this file
    1. import ex2
    2. call ex2.say_something()
%%file ex2.py

import logging

logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)

def say_something():
    logger.info('this is an informative message')


Overwriting ex2.py

### useful: run your ex2.py
import ex2
ex2.say_something()

Configuration

  1. setup
    1. change the level of ex2’s logger to DEBUG
    2. call ex2.say_something() - this should write the usual output

  2. Review this basic YAML configuration, and see that you understand how it will:
    1. set a simple format that is the same as the default format
    2. set a handler that logs to console
    3. connect the root logger to the console handler, with level WARNING
    4. modify the level for the ex2 logger to ERROR 
      version: 1
disable_existing_loggers: False
formatters:
  simple:
    format: '%(levelname)s:%(name)s:%(message)s'
handlers:
  console:
    class: logging.StreamHandler
    formatter: simple
    stream: ext://sys.stderr
loggers:
  ex2:
    level: ERROR
root:
  level: WARNING
  handlers: [console]



  3. load this configuration
    1. import the yaml module
    2. use yaml.load() to read this configuration into a dict object
    3. import logging.config module
    4. use logging.config.dictConfig() function to load the configuration from your dict


  4. execute ex2.say_something() again. this time there should not be any output. why?
import yaml
import logging.config

ex2.logger.setLevel(logging.DEBUG)
ex2.say_something()

config_string = """
version: 1
disable_existing_loggers: False
formatters:
  simple:
    format: '%(levelname)s:%(name)s:%(message)s'
handlers:
  console:
    class: logging.StreamHandler
    formatter: simple
    stream: ext://sys.stderr
loggers:
  ex2:
    level: ERROR
root:
  level: INFO
  handlers: [console]
"""

config_dict = yaml.safe_load(config_string)
logging.config.dictConfig(config_dict)

# now the log level is set to ERROR 
# so there should be no output from this logger
ex2.say_something()

Format #1

Copy the YAML configuration from the previous question, and change the formatter so that output from calling ex1.say_something() will look like this 2019-12-26 03:07:04,560 | WARNING | ex1 | this is a warning message

hints:

  • Read the LogRecord documentaion, which shows the attributes available for formatting
config_string = """
version: 1
disable_existing_loggers: False
formatters:
  simple:
    format: '%(asctime)s | %(levelname)s | %(name)s | %(message)s'
handlers:
  console:
    class: logging.StreamHandler
    formatter: simple
    stream: ext://sys.stderr
root:
  handlers: [console]
"""

config_dict = yaml.safe_load(config_string)
logging.config.dictConfig(config_dict)

ex1.say_something()

Format #2

Copy the YAML configuration from the previous question, and change the formatter so that output from calling ex1.say_something() will look like this:

2019-12-26 03:10:19,852 :: WARNING :: Module ex1 :: Line No 6 :: this is a warning message

config_string = """
version: 1
disable_existing_loggers: False
formatters:
  simple:
    format: '%(asctime)s :: %(levelname)s :: Module %(module)s :: Line No %(lineno)s :: %(message)s'
handlers:
  console:
    class: logging.StreamHandler
    formatter: simple
    stream: ext://sys.stderr
root:
  handlers: [console]
"""

config_dict = yaml.safe_load(config_string)
logging.config.dictConfig(config_dict)

ex1.say_something()

file handler

  • Use YAML configuration to
    1. set the levels of both ex1 and ex2 loggers to DEBUG
    2. setup file logging for ex2 logger so that it writes to ex2.log
  • test this by calling 
    ex1.say_something()
ex2.say_something()

    and reading ex2.log

from pathlib import Path

config_string = """
version: 1
disable_existing_loggers: False
formatters:
  simple:
    format: '%(asctime)s :: %(levelname)s :: Module %(module)s :: Line No %(lineno)s :: %(message)s'
handlers:
  console:
    class: logging.StreamHandler
    formatter: simple
    stream: ext://sys.stderr
  ex2:
    class: logging.FileHandler
    formatter: simple
    filename: ex2.log
    mode: 'w'
loggers:
  ex2:
    handlers: [ex2]
    level: DEBUG
  ex1:
    level: DEBUG
root:
  handlers: [console]
"""

config_dict = yaml.safe_load(config_string)
logging.config.dictConfig(config_dict)

ex1.say_something()
ex2.say_something()

print('ex2.log:', Path('ex2.log').read_text())


ex2.log: 2019-12-26 03:21:42,824 :: INFO :: Module ex2 :: Line No 8 :: this is an informative message


!dir


 Volume in drive E is New Volume
 Volume Serial Number is 5C7B-188A

 Directory of E:\dev\GitHub\learn-advanced-python\content\15_logging\exercise

26-Dec-19  03:18 AM    <DIR>          .
26-Dec-19  03:18 AM    <DIR>          ..
26-Dec-19  01:00 AM    <DIR>          .ipynb_checkpoints
26-Dec-19  03:06 AM               129 ex1.py
26-Dec-19  03:18 AM                 0 ex2.log
26-Dec-19  03:06 AM               165 ex2.py
26-Dec-19  01:14 AM               124 example.py
26-Dec-19  03:18 AM            30,516 solutions.ipynb
26-Dec-19  03:06 AM    <DIR>          __pycache__
               5 File(s)         30,934 bytes
               4 Dir(s)  3,086,822,178,816 bytes free