Creating multi-material unstructured mesh

Are there any Python examples available for creating a multi-material unstructured mesh for visualization? I would like to use vtk package for Anaconda Python, but would be open to others, especially something hdf5 based.

Each material region in my structure will have a different set of variables. Scalar variables would be stored on on vertices, and Vector variables would be stored on tetrahedral (3d) or triangle (2d) centers.