Logging in appJar
appJar makes use of Python's built in logging capabilities.
Logging works in a similar way to the print() function, except you also provide a parameter indicating the importance of the message - the logger will then only display messages of the right importance.
There are five levels of importance:
CRITICAL- a very serious problem, the GUI may well stopERROR- a more serious problem, preventing something from happeningWARNING- something unexpected happenedINFO- confirmation that things are working as expectedDEBUG- detailed diagnostic information
By default, appJar will only log messages of importance WARNING or above. And, by default, appJar will simply print them to the console (screen).
appJar provides some useful functions for logging:
.logMessage(msg, level)- log a message, of the specified importance.setLogLevel(level)- set the logging level, all messages of less importance than this will be ignored.setLogFile(fileName)- write all log messages to the named file, instead of the console
You can also use the following convenience functions for logging messages:
.critical(msg).error(msg).warn(msg).debug(msg).info(msg)
Logging to file
One of the benefits of using Python's logging capabilites, is the ability to have them logged to a file.
By setting a fileName, messages will no longer appear on the screen. Instead, they will be written to the named file.
The logLevel is also increased to DEBUG
External Logging
If you want to bypass the appJar functions, and use the logger directly in your code, simply request your own copy of the logger: logger = logging.getLogger("appJar").
You can then talk directly to the same logging mechanism that appJar uses.
How to use
The idea behind having different levels of logging, is that you don't have to remove all of your debug & testing messages. It is common to include lots of testing messages during development, and then remove them once we're satisfied the code is working. However, these might sometimes prove useful in the future, when trying to diagnose something that has gone wrong.
With logging, you can register those messages as DEBUG or INFO. Then set the logLevel to be INFO during development, and WARNING once development is complete. Then, if you ever need them, you can simply change the logLevel.