Tree structure in Python . . .

Replies to This Discussion

Permalink Reply by Giulio Piacentino on October 10, 2014 at 4:27am

Hi Thomas

trees are complicated to use successfully in Grasshopper, and even more so to use programmatically. Luckily, often they can be ignored by working on items or studying a better type of definition. Occasionally, though, you really have to work with them.

I still would like to point out that it might not be your case. Maybe there is another way to approach this entirely within your definition. Saying this, I assume you are trying to achieve something in particular with this lists of lists exercise, and not trying to just do this as a standalone drill.

Finally, please have a look at this discussion. Benjamin posted a NestedListToDataTree function that might help you. However, obviously copying a data structure after-the-fact will be slower than creating it from scratch. You can always use that and the rest of the code on that page as a sample of how to construct a tree.

I hope this helps,

Giulio
--
Giulio Piacentino
for Robert McNeel & Associates
giulio@mcneel.com

Permalink Reply by Thomas Perkov on October 19, 2014 at 9:00am

Hi Giulio

Thanks for the answer! I thought I had said it :-S .. hmm

Benjamins scripts works perfectly! 

I not sure how the list in list would be created? 

two for loops? one counting the number of branches (list in list) and the second one filling in the items.. How do i count the items in each branch? :-S 

e.g. something like: 

list = []
for i in range(>>>>pt. ItemCount )
    for j in range(pt.BranchCount):
        list.append([>>>> pt item in each branch [i] ])

Permalink Reply by djordje on October 19, 2014 at 10:42am

Hi Thomas,

You can use the dataTree.Branch method to retrieve the list from it.
Check the attached file.

Again, as Giulio mentioned, all of this could be done without messing with data trees, setting the input to "Item access" and letting grasshopper do the rest on its own.

Attachments:

• dataTree_to_pythonListofLists_to_dataTree.gh, 6 KB

Permalink Reply by Thomas Perkov on October 19, 2014 at 12:01pm

Ty djordje

That's just what I needed :-)

Permalink Reply by Davide Scialò on October 28, 2014 at 5:18am

hi giulio

trees are complicated, yes!

even the basic shift path of grasshopper is difficult for me.

i want to use it inside python and i think to use GH_PathOffset.OffsetPat but i don't know hoe to set it correctly.

i have:

objects (input object as datatree into python component) structure={A;B;...;V;Z}

i want to shift that path like that: {a;B}-->{A} but i don't want to use LexicalReplace but something like offsetpath.

can you explain me how do use it???thank you very much.

the approach to gh sdk and scripting in general is really difficult.