A simple global event emitter in Python

event.py

_callbacks = {}

class Event():

    @staticmethod
    def on(event_name, f):
        _callbacks[event_name] = _callbacks.get(event_name, []) + [f]
        return f

    @staticmethod
    def emit(event_name, *data):
        [f(*data) for f in _callbacks.get(event_name, [])]

    @staticmethod
    def off(event_name, f):
        _callbacks.get(event_name, []).remove(f)


if __name__ == "__main__":
    count = 0
    def addX(x):
        global count
        count += x

    Event.on('add', addX)
    assert('add' in _callbacks)

    Event.emit('add', 2)
    assert(count == 2)

    Event.off('add', addX)
    Event.emit('add', 2)
    assert(count == 2)