The message loop could take a number of other forms, including sockets, named pipes, DDE, and COM, but SendMessage would seem to be simplest, if only mIRC could use it too.
Actually, sockets would be the simplest, since there is native support for this in mIRC and it doesn't rely on any Win32 specific extensions on the other end. You get lucky in python with a Win32 API library in the stdlib, but not every language has this. Sockets are the common denominator here-- they are also widely used and supported, so it should be super easy to get started with a socket connection to your python code.
