decev 1.0.0

Event handlers with decorators

DECEV (decorator events) by @dantechguy

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

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
# pass list of event names
events = decev.EventHandler()

2. Add functions to events

Event functions cannot have any arguments

# 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

Methods can only have the self argument

# class decorator is required for methods to work
@events.cls
class MyClass:
    def __init__(self):
        print('initialised!')

    # add myMethod to LAST_EVENT
    @events.LAST_EVENT
    def myMethod(self):
        print('myMethod')

    # and unbound methods work too
    @events.LAST_EVENT
    def myOtherMethod():
        print('myOtherMethod')

# create instance of class        
myObject = MyClass()

4. Run events

print()
events.run('firstEvent')
print()
events.run('event_two')
print()
events.run('LAST_EVENT')

Which produces this:

> py main.py
initialised!

myOtherFunction
myFunction

myOtherFunction

myMethod
myOtherMethod

How it works

Any functions added with zero arguments are assumed to be regular functions, and are subscribed immediately to the event.

Any functions added with one argument are assumed to be methods (the argument being self), and are tagged with the events. The class decorator inserts some code into the class' __init__ method to automatically subscribe these tagged methods once an instance has been created.

The reason methods cannot be subscribed immediately, is that at the time of decorator execution no instance has been created, so the self parameter has not been filled, so the method is unbound and will not run properly. Therefore, the method can only be subscribed after instantiation.