logging.basicConfig(level=logging.INFO
                    filename="new.log",
                    filemode="a",
                    format="%(asctime)s - %(levelname)s: %(message)s"
                    )now I want to add a custom variable to format, such as appname,
 look up the usage of logging.info on the Internet, as follows: 
 logging.info (msg,  args,  * kwargs) 
 then I modify format="% (asctime) s -% (levelname) s:% (appname) s% (message) s"), add a% (appname) s, 
, and then run logging.info (msg, appname="xxx") with an error. 
how can I implement the above requirements?
