What is the proper context for working with material nodes?

Question

Trying to work with nodes in a ShaderNodeTree on a material I've just created, and I'm getting the dreaded "context is incorrect" error.

Here's some code I successfully ran in the Blender UI:

def test():
    C.window.workspace = D.workspaces['Shading']
    new_material = D.materials.new('color_ramp')
    new_material.use_nodes = True
    C.active_object.data.materials.append(new_material)
    C.window.screen.areas[3].type = 'NODE_EDITOR'
    C.window.screen.areas[3].ui_type = 'ShaderNodeTree'
    spaces = C.window.screen.areas[3].spaces
    return spaces[0]

With an object selected, this correctly switches the window, creates a new material, assigns it to the object, switches the area to the Node Editor, and even has the main node selected in the Node Editor area. Calling data = test() and then calling data returns:

bpy.data.screens['Scripting']...SpaceNodeEditor

and does not allow me to deselect the main node, nor does it allow me to add new nodes. From the code of the poll() function for nodes/node trees, I was able to see the context needs to be in the Node Editor and have a node tree selected. Calling data.node_tree in the UI correctly prints the node_tree, but interestingly enough my program I'm building does not.

Does anyone know the correct context for working with nodes/node trees?

EDIT: I added some print statements to the function to see if I could see what was going wrong with the context. Looks like it isn't changing the Workspace properly, which could I suppose be part of the issue? Even though it's in the Node Editor area...I'm not quite sure.

I recently posted regarding context.temp_override here but you will need to adjust for the shading area — Ratt, Aug 29 '23 at 22:38
you can read more about context override in https://blender.stackexchange.com/questions/6101/poll-failed-context-incorrect-example-bpy-ops-view3d-background-image-add and use NODE_EDITOR as the area type when overriding. for example you can easily deselect the nodes using this code — Harry McKenzie, Aug 30 '23 at 01:38
@HarryMcKenzie I'm getting a StopIteration error when I run that code, unfortunately. I know I need to do a temp_override, I just can't get the context correct. It seems to be ignoring me trying to set the proper context. — Devin Gardner, Aug 30 '23 at 10:20
@DevinGardner because one of the areas need to be the shader node open. — Harry McKenzie, Aug 30 '23 at 11:17
Calling bpy.context.window.screen.areas[3].type = 'NODE_EDITOR' and changing one of the areas to the Node Editor still does not allow it to run properly. — Devin Gardner, Aug 30 '23 at 11:21
This first test: https://pastebin.com/ktCmPd4g is what I'm running. This is the output: https://pastebin.com/4JrCvG9d — Devin Gardner, Aug 30 '23 at 11:26
@DevinGardner your code works fine on Blender 3.6 as long as one area is open with shader editor :) — Harry McKenzie, Aug 30 '23 at 11:32

Harry McKenzie · Accepted Answer · 2023-08-30T12:30:06.670

2

Similar issue with this thread that has the same unintuitive solution:

area.spaces.active.node_tree = nodes #add this line before the ops statement
bpy.ops.node.select(deselect_all=True)

edited Aug 30 '23 at 12:30

answered Aug 30 '23 at 12:16

Harry McKenzie

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What is the proper context for working with material nodes?

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