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Beautiful logging in Python

24 Oct 2017 | python

The logging module

Documentation

This module is extremely useful and has many unknown features.

Useful features (to be completed)

LogRecord attributes

  • Every message from the message is an object of type LogRecord.
  • This gives us access to very useful information, here are some of them:
Name Format Description
asctime %(asctime)s Human-readable time when the LogRecord was created. By default this is of the form ‘2003-07-08 16:49:45,896’ (the numbers after the comma are millisecond portion of the time).
levelname %(levelname)s Text logging level for the message (‘DEBUG’, ‘INFO’, ‘WARNING’, ‘ERROR’, ‘CRITICAL’).
filename %(filename)s Filename portion of pathname.
lineno %(lineno)d Source line number where the logging call was issued (if available).

Source: LogRecord-attributes

Defining loggers from yaml file

Instead of going through a long list of calls to the logging API, configuring your logger can be done from files.

YAML example

logging_conf.yaml

version: 1                                                                               
disable_existing_loggers: False                                                          
formatters:                                                                              
    simple:                                                                              
        format: "[%(asctime)s]%(name)s %(levelname)s(%(module)s %(lineno)d): %(message)s"
        datefmt: "%Z %Y-%m-%d %H:%M:%S"                                                  
                                                                                         
handlers:                                                                                
    console:                                                                             
        class: logging.StreamHandler                                                     
        level: INFO                                                                      
        formatter: simple                                                                
        stream: ext://sys.stdout                                                         
                                                                                         
loggers:                                                                                 
    my-logger:                                                                            
        level: INFO                                                                      
        handlers: [console]                                                              
        propagate: no

main.py

import yaml
import logging
import logging.config
with open("logging_conf.yaml") as f:                   
    logging.config.dictConfig(yaml.safe_load(f.read()))
LOGGER = logging.getLogger("my-logger")

LOGGER.info("Bonjour !")

Output:

$ python main.py

[CEST 2017-10-24 14:03:13]my-logger INFO(main 8): Bonjour !

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