PseudoStructure is the base class definition for a simple Python data object that provides excellent get/set speed (comparable to attribute access on a simple class object) as well as a minimal memory footprint (marginally larger than a list or tuple containing the field values, but significantly smaller than a simple class object having the fields as attributes).
The PseudoStructure class is easy to extend — in the simplest case, just define additional __slots__. Objects can be pickled/unpickled, and nesting of objects is fully supported. All features have been tested on CPython 2.4 - 3.3.
My Variations on a (data object) theme blog article goes into much more detail on the need for and evolution of the PseudoStructure class, and presents several alternative approaches for Python data/parameter objects. You can also discuss or critique PseudoStructure at ActiveState Code Recipes.