Classy Events

Pythonic event-driven programming.

Dependencies

Python 3.8, 3.9

Install

pip install classy-events

Usage

The main ingredient is an event handler instance:

from classy_events import EventHandler
event_handler = EventHandler()

You can register event listeners for events of any type. In this example we use string events. An event listener is a callable, like a function or a method. The registered event handlers for a specific event are called if that event is dispatched by the event handler. Any keyword arguments that accompany the event are passed to the event listeners.

Function listeners

The listener for the event "spam", no callbacks needed!

@event_handler.on("spam")
def spam(value):
    print(f"on 'spam': '{value}'")

When the "spam" event is dispatched from anywhere in the code, def spam will be called:

event_handler.dispatch("spam", value="ham and eggs")

Now on 'spam': 'ham and eggs' is printed.

Classy listeners

To use instance methods as listeners, only one extra step is needed:

class Spam:
    def __init__(self):
        event_handler.bind(self)

    @event_handler.on("classy_spam")
    def spam(self, value):
        print(f"on '{type(self).__name__}.spam': '{value}'")

spam_instance = Spam()

In __init__, the instance is bound to the handler. Note that this event_handler.bind call is not required to be within the __init__.

To see this in action, we dispatch the "classy_spam" event:

event_handler.dispatch("classy_spam", value="the classiest")

And we see the output on 'Spam.spam': 'the classiest'.