Python logging configuration best practices

Python logging is misconfigured: messages don't appear, go to wrong destinations, or have insufficient context.

Proper logging setup:

import logging
import sys

# Configure once at application entry point
def setup_logging(level='INFO'):
    logging.basicConfig(
        level=level,
        format='%(asctime)s %(levelname)s %(name)s: %(message)s',
        datefmt='%Y-%m-%d %H:%M:%S',
        handlers=[
            logging.StreamHandler(sys.stdout),
        ]
    )
    # Quiet noisy libraries
    logging.getLogger('urllib3').setLevel(logging.WARNING)
    logging.getLogger('botocore').setLevel(logging.WARNING)

# In each module: get a named logger
logger = logging.getLogger(__name__)

def process_order(order_id):
    logger.info('Processing order %s', order_id)
    try:
        result = charge(order_id)
        logger.info('Order %s charged successfully', order_id)
        return result
    except PaymentError as e:
        logger.error('Payment failed for order %s: %s', order_id, e)
        raise
    except Exception:
        logger.exception('Unexpected error processing order %s', order_id)
        # .exception() includes stack trace automatically
        raise

# For JSON structured logging in production
import json

class JSONFormatter(logging.Formatter):
    def format(self, record):
        return json.dumps({
            'timestamp': self.formatTime(record),
            'level': record.levelname,
            'logger': record.name,
            'message': record.getMessage(),
            'module': record.module,
            'line': record.lineno,
        })

Rules:

• Use logger.info('msg %s', var) not logger.info(f'msg {var}') (lazy formatting)
• Use logger.exception() in except blocks (includes traceback)
• Get logger per module with __name__
• Configure logging ONCE at entry point, not in libraries

Python's logging module is powerful but its configuration is confusing. Getting it right once means consistent, useful logs across the entire application.

Python applications needing proper logging setup