The gio library provides both synchronous and asynchronous interfaces for performing IO. Unfortunately, the two APIs require quite different programming styles, making it difficult to convert code written to the simpler synchronous API to the asynchronous one.
For C programs this is unavoidable, but for Python we should be able to do better. And if you're doing asynchronous event driven code in Python, it makes sense to look at Twisted. In particular, Twisted's Deferred objects can be quite helpful.