Did I find the right examples for you? yes no

All Samples(1)  |  Call(0)  |  Derive(0)  |  Import(1)
Place a "white" tree (mapping) over a "grey" tree (mapping).
Entries in white tree dominate entries in grey key.
White entries with value None mean "deleted entry".
All inserts/deletes/updates are effected only in the white
tree.

This version is designed specifically to work with ftree/dframe generator objects.

src/n/u/nucular-0.5/nucular/frames/fltree.py   nucular(Download)
import fTree
import dframe
import fshadowtree
import frameGenerators
import scatter