Why logpp?

logpp is a fairly simple module that contains some extensions for Python’s built in logging module. It provides a few facilities that allow you to pass extended information with logging messages.

The three principle components are listed below.

• logpp.logging.msg()

• logpp.logging.LogppMessage

• logpp.logging.LogppHandler

The module also provides the LogppMixin which you can use to provide standardized access to a logger via the LogppMixin.logger method.

Logging a Message

The example below has been expanded to make the components easier to see, but it’s actually a fairly simple one-liner. The msg() function takes a summary str and a detail object (which in the example is just a dictionary).

The function returns a LogppMessage which, when represented in str form is simply the summary.

logging.info(
    msg(
        'The weather is currently sunny with a temperature of 25°C.',
        {
            'conditions': 'sunny',
            'temperature': 25
        }
    )
)

Logging handlers that aren’t aware of the detail information should simply see the logpp message as the summary.

Handling Messages

If you’re using logpp, chances are you want to do something useful or clever with the detail information. To accomplish that you can create your own logging handler. If your custom handler is only interested in logpp messages, you can extend the LogppHandler and override the emit_logpp() method. The base class will perform checks to make sure that only logging messages that are instances of the LogppMessage class are passed to this method.

Putting It All Together

The sample below briefly demonstrates the creation of a custom log handler and should give you an idea of what to expect from such a facility.

import logging
from logpp.logging import msg, LogppMessage, LogppHandler


# Create a custom handler.
class CustomLogppHandler(LogppHandler):

    def emit_logpp(self, msg_: LogppMessage):
        print(f'SUMMARY: {msg_.summary}')
        print(f'DETAILS: {msg_.detail}')


logging.basicConfig(level=logging.INFO)
# Add the custom handler to the logger (just as you would with any handler).
logging.getLogger().addHandler(CustomLogppHandler())

# Log a message to be handled by the custom handler.
logging.info(
    msg(
        'The weather is currently sunny with a temperature of 25°C.',
        {
            'conditions': 'sunny',
            'temperature': 25
        }
    )
)

# Log a message that will be ignored by the custom handler.
logging.info('This message will be ignored by the custom handler.')

Using the LogppMixin

Let’s say you have a class that needs to log its activities. Often you’ll want to use a named logger. This can involve a few lines of boiler plate which can be a bit tedious to produce in every class. By extending the LogppMixin your class gains the logger() function which returns a logger with a name that reflects the name of the class (though you can override that behavior by adding a __loggername__ attribute to the class).

import logging
from logpp.logging import LogppMixin


# Just so we may demonstrate the use of the mixin, here's a base class
# that has nothing to do with logging from which we can inherit.
class SampleBaseClass(object):
    pass


# Now let's create a class that extends the sample base class, but
# which also mixes in the logging facility.
class LoggableClass(SampleBaseClass, LogppMixin):

    def log_something(self):
        self.logger().info('Hello world!')


# Set up basic logging
logging.basicConfig(level=logging.INFO)

# Create a new instance of the mixed-in class...
loggable = LoggableClass()
# ...and ask it to log something.
loggable.log_something()

Resources

Would you like to learn more? Check out the links below!

• Read the Docs

• Logging HOWTO

Authors

• Pat Daburu - Initial work - github

See also the list of contributors who participated in this project.

License

This project is licensed under the MIT License - see the LICENSE.md file for details