python logging pretty print pformat indent width line break

python_logging.py

import logging
import time
from pprint import pformat
# pretty print logs: https://stackoverflow.com/a/11093247/5628238
# pformat indent: https://stackoverflow.com/a/29469358/5628238
# (even needed when using %s string format): do not evaluate complex pformat when log level not printed: https://docs.python.org/3/library/logging.html#logging.Logger.isEnabledFor
# (wrong: complex variable string takes time nevertheless): https://reinout.vanrees.org/weblog/2015/06/05/logging-formatting.html
# https://stackoverflow.com/questions/13131400/logging-variable-data-with-new-format-string

# main script or module
import logging
logging.basicConfig(format='%(name)s:%(levelname)s:%(message)s') # do not set global level, because otherwise everything gets logged
logger = logging.getLogger(__name__) # get logger with name of current module (gets value __main__ for main script)
# logger_module_xy = logging.getLogger('<module_name>') # get logger of current module
logger.setLevel(logging.DEBUG)
# logger_module_xy.setLevel(logging.INFO) # (for example)

#
#

logger.debug('Hi')
#
#

logger.setLevel(logging.INFO)

def get_complex_log_message():
    time.sleep(3)
    return {"object_after": "three seconds"}

start_time = time.time()
logger.info("Start time: %s", start_time)
logger.debug("%s",get_complex_log_message()) # this part takes 3 seconds even when it is not printed
end_time = time.time()
logger.info("End time: %s", end_time)
logger.info("--- It took %s seconds ---", (end_time - start_time))

# thats why it is a good idea to encapsulate pformat strings for complex objects in this if clause:

complex_object = {"x": {"xx": 11, "xy": 12},"y": 2,"z": 3}

if logger.isEnabledFor(logging.DEBUG):
    logger.info('this gets only evaluated when logging level is set to debug even when this is set to info')
    
    # this more complex logging command width pformat is only evaluated when logging level is set to debug
    # print pretty formated string in new line for better readability, 
    # width=1 forces linebreaks, width=30 forces less linebreaks and so on
    logger.debug("\n%s",pformat(complex_object,indent=1,width=1))