[Medium] Stop Using Print! Python Logging for Data Scientists

00 Python Logging for Data Scientists.md

Stop Using Print! Python Logging for Data Scientists

Code snippets for the Medium post: Link

01_basic_config.py

import logging

# Setup Basic Configuration
logging.basicConfig(level=logging.INFO,
                    format='%(asctime)s %(levelname)s: %(message)s',
                    datefmt='%Y-%m-%d %H:%M:%S')

02_get_logger.py

# Instantiate the Logger
LOGGER_NAME = 'main'
logger = logging.getLogger(LOGGER_NAME)

03_file_handler.py

# Create file handler and set level to custom level above CRITICAL
METRICS = 60
logging.addLevelName(METRICS, 'METRICS')
file_handler = logging.FileHandler('metrics.log')
file_handler.setLevel(METRICS)
 
# Add file handler to logger
logger.addHandler(file_handler)

constants.py

# Create a custom logging level called "METRICS" with a value 60
# 60 is higher than CRITICAL logging. 
# This ensures no other log levels write to file
METRICS = 60

# Unique name for the logger
LOGGER_NAME = 'main'

main.py

import constants as cst
import logging
import test_print

# Setup Basic Configuration
logging.basicConfig(level=logging.INFO,
                    format='%(asctime)s %(levelname)s: %(message)s',
                    datefmt='%Y-%m-%d %H:%M:%S')

# Instantiate the Logger
logger = logging.getLogger(cst.LOGGER_NAME)

# Create file handler and set level to custom level above CRITICAL
logging.addLevelName(cst.METRICS, 'METRICS')
file_handler = logging.FileHandler('metrics.log')
file_handler.setLevel(cst.METRICS)

# Add file handler to logger
logger.addHandler(file_handler)

if __name__ == '__main__':
    # Test out the logger from the original script
    logger.info(
        'This message is displayed on the terminal but NOT written to file')
    logger.log(
        cst.METRICS,
        'This message is both displayed on the terminal AND written to file')

    # Test out the logger in an imported function
    test_print.test_print()

test_print.py

import constants as cst
import logging

# Instantiate the same logger
logger = logging.getLogger(cst.LOGGER_NAME)

def test_print():
    logger.log(cst.METRICS, 'This also writes to file!')