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Classes and Functions

So far, we have seen the default logger named root, which is used by the logging module whenever its functions are called directly like this: logging.debug(). You can (and should) define your own logger by creating an object of the Logger class, especially if your application has multiple modules. Let’s have a look at some of the classes and functions in the module.

The most commonly used classes defined in the logging module are the following:

  • Logger: This is the class whose objects will be used in the application code directly to call the functions.

  • LogRecord: Loggers automatically create LogRecord objects that have all the information related to the event being logged, like the name of the logger, the function, the line number, the message, and more.

  • Handler: Handlers send the LogRecord to the required output destination, like the console or a file. Handler is a base for subclasses like StreamHandler, FileHandler, SMTPHandler, HTTPHandler, and more. These subclasses send the logging outputs to corresponding destinations, like sys.stdout or a disk file.

  • Formatter: This is where you specify the format of the output by specifying a string format that lists out the attributes that the output should contain.

Out of these, we mostly deal with the objects of the Logger class, which are instantiated using the module-level function logging.getLogger(name). Multiple calls to getLogger() with the same name will return a reference to the same Logger object, which saves us from passing the logger objects to every part where it’s needed. Here’s an example:

import logging

logger = logging.getLogger('example_logger')
logger.warning('This is a warning')

This is what you’d get:

This is a warning

Comments & Discussion

Kalesis on July 30, 2019

Hello, in the video the code is wrong. Dice “logging” instead of “logger”. regards

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