Today we’re going to talk about the most underrated feature in Python: its logging module. You might be thinking, “Who needs a fancy logging system when I can just print stuff to the console?” Well, my friend, let me tell you why you should give this bad boy a chance.
To start, let’s import the logging module and create our logger object. This is where we set up our log configuration:
# Import the logging module
import logging
# Create a logger object with the name of the current module
logger = logging.getLogger(__name__)
# The logger object will be used to log messages and errors throughout the script
# It is important to give it a unique name to easily identify where the logs are coming from
The `__name__` variable automatically sets the name of your current script or module, which makes it easier to organize your logs by file or function. You can also create a logger object for each component in your application if you want more granularity.
Now that we have our logger set up, let’s log some stuff! Here are the basic logging levels:
– `debug` (lowest): Detailed information, typically of interest only when diagnosing problems.
– `info`: Informational messages that highlight the progress of the application but are not essential to its operation.
– `warning`: An indication that something unexpected happened or indicative of some problem in the near future (e.g., ‘disk space low’).
– `error`: Due to a more serious problem, the application may not be able to continue running.
– `critical`: A critical error, indicating that the application itself should be shut down.
To log messages at different levels, you can use the logger’s methods with appropriate arguments. For example:
# Import the logging module
import logging
# Create a logger object
logger = logging.getLogger()
# Set the logging level to DEBUG
logger.setLevel(logging.DEBUG)
# Create a console handler and set its level to DEBUG
console_handler = logging.StreamHandler()
console_handler.setLevel(logging.DEBUG)
# Create a formatter and add it to the console handler
formatter = logging.Formatter('%(levelname)s - %(message)s')
console_handler.setFormatter(formatter)
# Add the console handler to the logger
logger.addHandler(console_handler)
# Log messages at different levels
logger.debug('This is a debug message') # Prints a debug message to the console
logger.info('This is an info message') # Prints an info message to the console
logger.warning('This is a warning message') # Prints a warning message to the console
logger.error('This is an error message') # Prints an error message to the console
logger.critical('This is a critical error!') # Prints a critical error message to the console and stops the application from running
# Explanation:
# The script imports the logging module and creates a logger object.
# The logging level is set to DEBUG, which means all messages at or above this level will be logged.
# A console handler is created and its level is set to DEBUG as well.
# A formatter is created and added to the console handler to format the log messages.
# The console handler is then added to the logger.
# Finally, the script logs messages at different levels using the logger's methods.
# The debug, info, and warning messages will be printed to the console, while the error and critical messages will also be printed and stop the application from running.
You can also format your messages using string formatting or the `str.format()` method:
# Define variables for name and age
name = 'John Doe'
age = 30
# Use string formatting to insert the values of name and age into the message
# and pass it as an argument to the logger.info() function
logger.info("Hello, {}! You are {} years old.".format(name, age))
# The logger.info() function logs the formatted message to the console or a log file.
The logging module also supports handlers that allow you to send your log messages to different destinations like files or email. Here’s an example:
# Import the logging module
import logging
# Import the FileHandler class from the logging module
from logging import FileHandler
# Create a logger object with the name of the current module
logger = logging.getLogger(__name__)
# Create a FileHandler object to handle the log messages and specify the file name
handler = FileHandler('mylogfile.txt')
# Create a formatter object to specify the format of the log messages
formatter = logging.Formatter("%(asctime)s %(levelname)s %(message)s")
# Set the level of the FileHandler to DEBUG
handler.setLevel(logging.DEBUG)
# Set the formatter for the FileHandler
handler.setFormatter(formatter)
# Add the FileHandler to the logger object
logger.addHandler(handler)
# Log some messages!
# Log a debug message
logger.debug('This is a debug message')
# Log an info message
logger.info('This is an info message')
# The logging module allows you to send log messages to different destinations like files or email.
# Here, we create a logger object with the name of the current module and a FileHandler object to handle the log messages.
# We also specify a formatter to format the log messages and add the FileHandler to the logger object.
# Finally, we log some messages using the logger object.
In this example, we’re creating a new handler object (a `FileHandler`) and setting its level to `DEBUG`. We also set the formatter for our log messages using the `setFormatter()` method. Finally, we add the handler to our logger with the `addHandler()` method.
That’s it! You now have a basic understanding of Python’s logging module and how to use it in your code.