Manual

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 logpp.logging.LogppMixin which you can use to provide standardized access to a logger via the logpp.logging.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 logpp.logging.msg() function takes a summary str and a detail object (which in the example is just a dictionary).

The function returns a logpp.logging.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 logpp.logging.LogppHandler and override the logpp.logging.LogppHandler.emit_logpp() method. The base class will perform checks to make sure that only logging messages that are instances of the logpp.logging.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 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 logpp.logging.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 logpp.logging.LogppMixin your class gains the logpp.logging.LogppMixin.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 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()