Portable Channel Access Server (PCAS) library exists along with database channel access server (RSRV) in EPICS base. PCAS provides several C++ classes (server tool), making use of abstract callback methods, to let server application respond to channel access clients requests. Due to the intrinsic complexity of C++ and channel access request/data handling, this is not widely used among EPICS developers.
Python is a language easy enough to get in quickly while possessing rich standard libraries and numerous extensions. This makes it very attractive to prototype a PCAS application in Python.