How to access shader node via Python script? [duplicate]

Question

Above is the material I've created. I exported my model to .obj from Blender. From a Python script (I have Blender compiled as a Python Module), I import my .obj file. I then attempt to set the Noise Texture 'W' property:

import bpy

bpy.ops.import_scene.obj( filepath = PATH_TO_MY_OBJ)
bpy.context.object.name = "obbb"
obj = bpy.data.objects["obbb"]

My material is called Material. How can I access the Noise Texture node and change the value of W?

As suggested, here is the Blend file:

Answer 1

Above is the material I've created. I exported my model to .obj from Blender. From a Python script (I have Blender compiled as a Python Module), I import my .obj file. I then attempt to set the Noise Texture 'W' property:

When you rountrip through OBJ you will not get the original node graph back. OBJ only supports a few simple material properties, not stuff like noise textures. Import your .obj into Blender and check the shader graph. You will see that all those nodes you added are lost. That's why there isn't a noise texture.

See Import & Export of Node Shaders in the manual for more info about what is supported when exporting to OBJ.

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Here is how you can append (as in File > Append) the CloudCube from your proceedural_clouds.blend file into the current file and change its W.

import bpy

# First, append the CloudCube from your .blend into the current file.
blendpath = "//proceedural_clouds.blend"
with bpy.data.libraries.load(blendpath, link=False) as (data_src, data_dst):
    data_dst.objects = ["CloudCube"]
cloud_cube = data_dst.objects[0]

# Link cloud cube into scene so it shows up
bpy.context.scene.collection.objects.link(cloud_cube)

# Grab the material it uses
mat = cloud_cube.material_slots[0].material

# Change W
mat.node_tree.nodes["Noise Texture"].inputs["W"].default_value = 42.0

Answer 2

Hover over the W property and right-click (RMB context) menu Copy Full Data Path:

Then you can paste it into your python script, e.g.,:

bpy.data.materials["Material.001"].node_tree.nodes["Noise Texture"].inputs[1].default_value

and just add = 0.2 or whatever

Answer 3

EDIT The real reason is that the object file was being imported as OBJ, which doesn't support Blender materials, especially not noise.

The solution is to either read the Blender file or to reconstruct the material in Python before trying the solution below.

Your approach was close:

from random import randrange
import bpy
import time


for i in range(0,50):
    n = randrange(10)
    bpy.data.materials["Material"].node_tree.nodes["Noise Texture"].inputs[1].default_value = n

but you need to change the last line slightly:

bpy.data.materials["CloudMaterial"].node_tree.nodes["Noise Texture"].inputs['W'].default_value = n

The index for materials should be the actual name of the material and using ['W'] rather than [1] makes the code work even if the developers change the order of input sockets in the future.

Answer 4

You wrote "I have Blender compiled as a Python Module". Do you realize that you can run blender in background against a script (no UI).

For example I set up a python script.py as

import bpy
bpy.data.materials['CloudMaterial'].node_tree.nodes['Noise Texture'].inputs[1].default_value=2.33
bpy.ops.wm.save_mainfile()

and used the command line:

blender -b proceedural_clouds.blend -P script.py

And the V value was changed.