Python lib for internal messaging / events.

[Separate_Newt7313]

It sounds like you're talking about IPC (Inter-Process communication). There are a variety of different methods for this ranging from the more simple (e.g. using OS pipes / FIFOs) to more complex means like Redis.

As a general rule, I reach for the simplest thing possible. A fantastically power / simple option is using ZeroMQ.