Lazy logger message string evaluation

Question

I\'m using standard python logging module in my python application:

import logging
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(\"log\")
whi         


        

Answer 1

import logging
import time

logging.basicConfig(level=logging.INFO)
logger = logging.getLogger("log")

class Lazy(object):
    def __init__(self,func):
        self.func=func
    def __str__(self):
        return self.func()

logger.debug(Lazy(lambda: time.sleep(20)))

logger.info(Lazy(lambda: "Stupid log message " + ' '.join([str(i) for i in range(20)])))
# INFO:log:Stupid log message 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

If you run the script, you'll notice the first logger.debug command does not take 20 seconds to execute. This shows the argument is not evaluated when the logging level is below the set level.