The zope.event package provides a simple event system, including:
- An event publishing API, intended for use by applications which
  are unaware of any subscribers to their events.
- A very simple event-dispatching system on which more sophisticated
  event dispatching systems can be built. For example, a type-based
  event dispatching system that builds on zope.event can be found
  in zope.component.

Homepage:
https://github.com/zopefoundation/zope.event
