decev 1.2.0

Event handlers with decorators

DECEV (decorator events) by @dantechguy

A teeny library for event handling which uses decorators for event subscription

Overview

• Add functions to events with the @event.your_event decorator
• Add instance methods to events with the @decev.cls class decorator and then the @event.m.your_event or @event.method.your_eventmethod decorator
• Run events with event.run('your_event')
• Pass arguments with events with event.run('your_event', 'bar', foo=True)

Installation

Either copy decev/decev.py into your directory, or run

pip install decev

then import into your file with import decev

Usage

1. Create an EventHandler object

import decev
events = decev.EventHandler()

2. Add functions to events

A single function can have multiple events

# add myFunction to firstEvent
@events.firstEvent
def myFunction():
    print('myFunction')

# add myOtherFunction to firstEvent and event_two
@events.firstEvent
@events.event_two
def myOtherFunction():
    print('myOtherFunction')

3. Add methods to events

Use the @decev.cls class decorator and @events.m.your_event to add methods with a self parameter

@decev.cls
class MyClass:      
    # add myMethod to THIRD_EVENT
    @events.m.THIRD_EVENT
    def myMethod(self):
        print('myMethod')

    # add unbound myOtherMethod to THIRD_EVENT
    @events.THIRD_EVENT
    def myOtherMethod():
        print('myOtherMethod')

# create instance of class        
myObject = MyClass()

4. Receive arguments in callbacks

Make sure the parameters match the arguments passed into events.run()

@events.ArgEvent
def myArgFunction(foo, bar=True):
    print(f'myArgFunction foo={foo} bar={bar}')

5. Run events

events.run('firstEvent')
print()
events.run('event_two')
print()
events.run('LAST_EVENT')
print()
events.run('ArgEvent', 100, bar=False)

Which produces this:

> py main.py
myOtherFunction
myFunction

myOtherFunction

myOtherMethod
myMethod

myArgFunction foo=100 bar=False

How it works

All functions added with @events.your_event are subscribed immediately to events's callback dictionary.

As instance methods require the self parameter, they can only be subscribed once the class has been instantiated and self has a value. The alternate @events.m.your_event syntax instead tags the method, storing the event names and event handler. The @decev.cls class decorator then inserts a code snippet into the object's __init__ method to subscribe the events on instantiation.