observable

pyobservable is a minimalist event system for python. It provides you an easy-to-use interface to trigger arbitrary functions when specific events occur.

from observable import Observable

obs = Observable()

@obs.on("error")
def error_handler(message):
    # do some fancy error handling
    logging.error(f"An error occured: {message}")

...

def do_time_travel():
    # do some time traveling
    ...
    if year != 1291:
        obs.trigger("error", "Time travel to 1291 didn't work")

Note: We are Python 3 only! Only Python Versions >= 3.5 are supported. Use v0.3.2 for older Python Versions.

How to use

Use a pip to install it from PyPI:

pip install observable

After completion you can start using observable:

from observable import Observable

obs = Observable()

Usage

on: Register event handler with on

There are two ways to register a function to an event.
The first way is to register the event with a decorator like this:

@obs.on("error")
def error_func(message):
    print("Error: %s" % message)

The second way is to register it with a method call:

def error_func(message):
    print("Error: %s" % message)
obs.on("error", error_func)

once: Register event handler with once

once works like on, but once the event handler is triggered it will be removed and cannot be triggered again.

trigger: trigger event

You can trigger a registered event with the trigger method:

obs.trigger("error", "This is my error message")

If no handler for the event error could be found an Observable.NoHandlerFound-Exception will be raised.

off: remove handler and events

Remove a handler from a specified event:

obs.off("error", error_func)

obs.off("error", [error_func, second_error_func])

Remove all handlers from a specified event:

obs.off("error")

Clear all events:

obs.off()

get_all_handlers, get_handlers and is_registered: Check which handlers are registered

Imagine you registered the following handlers:

@obs.on("success")
def success_func():
    print("Success!")

@obs.on("error")
def error_func(message):
    print("Error: %s" % message)

Then you can do the following to inspect the registered handlers:

>>> obs.get_all_handlers()
{'success': [<function success_func at 0x7f7f32d0a1e0>], 'error': [<function error_func at 0x7f7f32d0a268>]}
>>> obs.get_handlers("success")
[<function success_func at 0x7f7f32d0a1e0>]
>>> obs.get_handlers("other_event")
[]

This project is published under MIT.
A Timo Furrer project.
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