Today we’re gonna talk about something that every Python developer should know how to do logging. But not just any kind of logging, oh no. We’re talking about the best practices for logging in your Python libraries. Because let’s face it, if you don’t have good logs, what’s the point of having a library at all?

To kick things off, use the logging module. This is the go-to option for most Python developers because it’s well maintained and backed by a huge community that will always have an answer to your doubts. Plus, it comes with six different levels of messages each designed for a specific purpose. So stick to them!

Now timestamps. This is a critical feature of logs that print functions don’t have. In addition to knowing where a problem appeared, it’s important to know when it happened. Timestamps are your biggest allies in these situations. Make sure to use the standard format ISO-8601 because who wants to deal with weird time formats?

Here’s an example of how you can log something using Python’s logging module:

# Import the logging module
import logging

# Create a logger object with the name of the current module
logger = logging.getLogger(__name__)

# Create a formatter object with the desired format for the log messages
formatter = logging.Formatter('%(asctime)s %(levelname)s %(message)s')

# Create a file handler object to write the log messages to a file
handler = logging.FileHandler('my_log.txt', mode='a')

# Set the level of the handler to DEBUG, meaning it will log all messages
handler.setLevel(logging.DEBUG)

# Set the formatter for the handler to the previously created formatter object
handler.setFormatter(formatter)

# Add the handler to the logger object
logger.addHandler(handler)

# Log a debug message using the logger object
logger.debug("This is a debug message")

# The purpose of this script is to create a logger object and use it to log a debug message to a file. 
# The logging module is imported to enable logging functionality. 
# A logger object is created with the name of the current module, which will be used to identify the source of the log messages. 
# A formatter object is created with the desired format for the log messages. 
# A file handler object is created to write the log messages to a file, with the mode set to 'a' to append new messages to the existing file. 
# The level of the handler is set to DEBUG, meaning it will log all messages. 
# The formatter is set for the handler. 
# Finally, the handler is added to the logger object. 
# A debug message is then logged using the logger object.

In this example, we’re creating a logger object and setting up a file handler to log our messages. We’re also using the `%(asctime)s` format string to include timestamps in our logs. And finally, we’re logging a debug message with the `logger.debug()` function.

You can also use the logging library’s built-in features to add additional context to your logs, such as log levels and exception stack traces. This is especially useful when you want to troubleshoot issues in your code.

Remember to always include timestamps, stick to the six different message levels, and use a consistent format. And if you’re feeling fancy, add some context with log levels and exception stack traces.