The ZODB is an object-oriented database written in Python and optimized in C. Just subclass off of class Persistent Object, and Persistent Container, and your objects, graphs and aplications become persistent.
The ZODB Demo makes it very easy to start building your own application. You can start by customizing the TreeLeaf and the TreeBranch classes. Then you can perform CRUD on those objects.
The demo includes traditional relational CRUD, Create, Read, Update, and Delete. But it also includes the extended graph CRUD. Rename an Object. Cut and paste leaves or branches, copy and paste leaves or branches. The talk also demonstrates the soon-to-be released view and restore historic versions.
It is easy to start using the ZODB. It is old, mature, and rock solid. It is heavily used in Plone and Pyramid.
Zopache IDE Demo
Here is a demo of the Zopache IDE.