I have a C++ process running in the background that will be generating 'events' infrequently that a Python process running on the same box will need to pick up.

The code on the C side needs to be as lightweight as possible.  
The Python side is read-only.
The implementation must be cross-platform.
The data being sent is very simple.

What are my options?
Thanks
How complex is your data? If it is simple I would serialize it as a string. If it was moderately complex I would use JSON. TCP is a good cross-platform IPC transport. Since you say that this IPC is rare the performance isn't very important, and TCP+JSON will be fine.
Simple IPC between C++ and Python (cross platform)