The Blender API provides us with the means to define IPOs from scratch, enabling the definition of movements not easily re-created by setting key frames by hand. Thus there is more to IPOs than just driving one IPO by another one. Furthermore, Shape keys and poses are examples of (collections of) IPOs that are quite different from, for example, a location IPO. We will encounter both shape keys and poses later on in this article, but we will start off with looking at how we might define an IPO from scratch.
The Python integration into Blender is an evolving subject. Therefore, all we can give you here just a quick overview of the possibilities of Python in Blender.
The new API is closer to the data structure of Blender. It is strongly oriented on what you can visualize in the OopsWindow. There are classes for Scene, Object, Mesh, Curve etc., and functions to connect and create them.