Logging is the process of recording information (usually in text format) during runtime for debugging and troubleshooting purposes. Its like having a personal assistant that keeps track of everything your code does, so you can go back and see what went wrong when things inevitably break down. And with Python’s built-in logging module, it’s easier than ever to set up!
But let’s be real here: configuring loggers is not exactly the most thrilling task in the world. Its like trying to read a novel written entirely in technical jargon and acronyms. Who needs that kind of stress? Well, lucky for us, Python has got our backs!
Before anything else, let’s import the logging module:
# Import the logging module
import logging
# Configure the root logger to output all messages to the console
logging.basicConfig(level=logging.DEBUG)
# Create a custom logger named 'my_logger'
my_logger = logging.getLogger('my_logger')
# Set the logging level for 'my_logger' to DEBUG
my_logger.setLevel(logging.DEBUG)
# Create a file handler to output logs to a file named 'my_logs.txt'
file_handler = logging.FileHandler('my_logs.txt')
# Set the logging level for the file handler to INFO
file_handler.setLevel(logging.INFO)
# Create a formatter to format the log messages
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
# Add the formatter to the file handler
file_handler.setFormatter(formatter)
# Add the file handler to the custom logger
my_logger.addHandler(file_handler)
# Log a debug message
my_logger.debug('This is a debug message')
# Log an info message
my_logger.info('This is an info message')
# Log a warning message
my_logger.warning('This is a warning message')
# Log an error message
my_logger.error('This is an error message')
# Log a critical message
my_logger.critical('This is a critical message')
# Close the file handler
file_handler.close()
# Remove the file handler from the custom logger
my_logger.removeHandler(file_handler)
# Log a new message after removing the file handler
my_logger.info('This is a new info message')
Now we can create a logger object by calling `logging.getLogger()`. This will return an instance that we can customize to suit our needs. For example:
# Creating a logger object using the logging module
# This will allow us to customize our logging settings
# Importing the logging module
import logging
# Creating a logger object and assigning it to the variable "logger"
# The __name__ attribute will be used to identify the logger
logger = logging.getLogger(__name__)
# The getLogger() function returns an instance of the logger class
# This instance can be customized to suit our needs
# For example, we can set the logging level to DEBUG
# This will allow us to see all log messages, including those with lower levels
logger.setLevel(logging.DEBUG)
# We can also add a handler to the logger
# This will determine where the log messages will be outputted
# In this case, we will use a StreamHandler to output the messages to the console
handler = logging.StreamHandler()
logger.addHandler(handler)
# Now we can use the logger to log messages at different levels
# For example, we can use the debug() method to log a message with the DEBUG level
logger.debug("This is a debug message")
# We can also use the info() method to log a message with the INFO level
logger.info("This is an info message")
# And we can use the error() method to log a message with the ERROR level
logger.error("This is an error message")
# The logger will only output messages that are at or above the set logging level
# In this case, all three messages will be outputted to the console
This line sets up the logger with the name of the current module (which is handy for keeping track of which part of your code is generating logs). But what if we want to log at different levels? Maybe we only care about errors and warnings, or maybe we want to see every single thing that happens. Well, Python has got us covered there too!
Logging supports five different levels: DEBUG (most detailed), INFO, WARNING, ERROR, and CRITICAL (most severe). To set the logging level for our logger object, we can use a dictionary-like syntax to specify which levels should be logged. For example:
# Import the logging module
import logging
# Create a logger object with the name of the current module
logger = logging.getLogger(__name__)
# Set the logging level for the logger object to DEBUG
logger.setLevel(logging.DEBUG)
# The logger object will now log all messages with a level of DEBUG or higher
# This means that all messages, regardless of their severity, will be logged
# This is useful for debugging purposes, as it provides the most detailed information
# However, we can also specify which levels should be logged using a dictionary-like syntax
# In this case, we are setting the logging level to DEBUG, which will log all messages
# with a level of DEBUG or higher
# Other available levels are INFO, WARNING, ERROR, and CRITICAL
# This allows us to control the amount of information that is logged, depending on our needs
This will log everything at DEBUG level and higher (INFO, WARNING, ERROR, CRITICAL). But what if we only want to see errors? We can set the logger’s level to `ERROR`, like so:
# Import the logging module
import logging
# Create a logger object with the name of the current module
logger = logging.getLogger(__name__)
# Set the logger's level to ERROR, meaning it will only log messages at ERROR level and higher
logger.setLevel(logging.ERROR)
Now handlers, which are responsible for actually writing log messages to a file or console (or wherever else you want them). Python provides several built-in handler classes that we can use: `StreamHandler`, `FileHandler`, and more! For example:
# Import the logging module
import logging
# Create a logger object with the name of the current module
logger = logging.getLogger(__name__)
# Set the logging level to ERROR, which will only log messages with a severity level of ERROR or higher
logger.setLevel(logging.ERROR)
# Create a handler object to handle the logging output
handler = logging.StreamHandler() # This handler will write log messages to the console
# Create a formatter object to format the log messages
formatter = logging.Formatter('%(asctime)s %(levelname)s %(message)s')
# Set the formatter for the handler
handler.setFormatter(formatter)
# Add the handler to the logger
logger.addHandler(handler)
# Now the logger is ready to use, and any log messages with a severity level of ERROR or higher will be written to the console.
This code sets up a logger with an error level, and adds a `StreamHandler` that writes to the console using a custom formatting string (which includes the date/time, log level, and message). With just a few lines of code, we’ve set up logging in our Python application. It might not be as exciting as building a web scraper or creating a machine learning model, but trust me when I say that having good logging practices can save us hours (or even days) of debugging time down the line!
So go ahead and embrace the power of Python’s built-in logging module. And always remember: when in doubt, just log it out!