Python Logging: Basic Tutorial and Template

The python logging module enables developers to track and troubleshoot program issues. When developing a software application, it’s essential to have a way to track issues and errors that may take place throughout the application development procedure.

The logging module provides a way to record events and messages from a particular code, allowing us to track down issues and troubleshoot problems as they arise.

In summary, the logging module aids the following:

• Recording events and messages from code
• Setting different levels of logging $\rightarrow$ DEBUG, INFO, WARNING, and ERROR
• Customizing the format of log messages
• Stores log messages to a file, console, or network socket

Basic Logging with basicConfig()

The simplest way to use the logging module is to call the basicConfig() function. Here’s an example template we can use in a code:

import logging

logging.basicConfig(level=logging.DEBUG, format='%(asctime)s %(levelname)s %(message)s')

This configurations sets the logging level to DEBUG, which means that all log messages at the DEBUG level or higher will be recorded. The format parameter specifies the predefined format of the log messages. In this example, we record the timestamp, level name, and message.

Here’s how we can use different levels of log messages:

import logging

logging.debug('This is a debug message')
logging.info('This is an info message')
logging.warning('This is a warning message')
logging.error('This is an error message')
logging.critical('This is a critical message')

While using the basicConfig() function is the simplest way to use the logging module, it has some limitations. One major issue may arise when we import another file that includes logging.basicConfig() as well.

Logging with Loggers, Handlers, and Formatters

We can use loggers, handlers, and formatters to overcome the limitations of basicConfig(). This allows us to separate different parts of our working code into distinct logging namespaces, direct log messages to different destinations (files), and customize the formatting of log messages.

First, we need to use the getLogger() function, which takes a string name as its argument:

import logging
logger = logging.getLogger(__name__)

Plz, note that, the logger’s name should match the name of the module or class it represents.

Handlers

A handler is an object that sends log messages to a specific destination, such as a file, console, or network socket. We can use handlers to direct log messages to different destinations.

We can use StreamHandler, FileHandler, or SocketHandler, depending on the type of destination we want to send the log messages to. Most of the time we use FileHandler. For example,

import  logging

file_handler = logging.FileHandler('demo_logs.log')
file_handler.setLevel(logging.DEBUG)
file_handler.setFormatter(formatter)

Formatters

A formatter is an object that specifies the format of log messages. We can use formatters to customize the format of log messages. here’s an example,

import logging
formatter = logging.Formatter('%(asctime)s %(levelname)s %(message)s')

Full Examples

Here’s an example for stream handler:

import logging

logger = logging.getLogger(__name__)
console_handler = logging.StreamHandler()
formatter = logging.Formatter('%(asctime)s %(levelname)s %(message)s')

console_handler.setFormatter(formatter)
logger.addHandler(console_handler)
logger.setLevel(logging.DEBUG)

An example from Corey Schafer’s Code Snippet that includes both file and stream handler:

import logging

logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)

formatter = logging.Formatter('%(asctime)s:%(name)s:%(message)s')

file_handler = logging.FileHandler('demo_logs.log')
file_handler.setLevel(logging.ERROR)
file_handler.setFormatter(formatter)

stream_handler = logging.StreamHandler()
stream_handler.setFormatter(formatter)

logger.addHandler(file_handler)
logger.addHandler(stream_handler)

In this tutorial, we’ve explored how to use the Python logging module to add logging capabilities to our code. We’ve covered the basics of logging with basicConfig(), as well as the more advanced techniques of loggers, handlers, and formatters.

That’s all for today! Have a good day, cheers!!! 😎