How to create a custom data tree?

[AndersDeleuran]

You probably want the AddRange method, see an example here. Also Giulio’s link further up to the official McNeel GHPython DataTree docs:

Tree operations in Python

There’s also the documentation of the DataTree class itself: https://developer.rhino3d.com/wip/api/grasshopper/html/T_Grasshopper_DataTree_1.htm And some minimal examples for reading and writing two dimensional trees: Read: """ Read the Grasshopper Datatree "FooTree" and translates it to a nested Python list """ pyList = [list(b) for b in FooTree.Branches] Write: import Grasshopper as gh def listToTree(nestedList): """ Convert a nested python iterable to a datatree """ …