working code to change parameter of roughness for x given mat selections

import c4d
import maxon
from maxon import GraphDescription

doc = c4d.documents.GetActiveDocument()

# Get selected materials directly
selected_materials = doc.GetActiveMaterials()

# Modify roughness for each selected material
for material in selected_materials:
    graph = GraphDescription.GetGraph(material, 
                                      nodeSpaceId=maxon.NodeSpaceIdentifiers.RedshiftMaterial)
    
    GraphDescription.ApplyDescription(graph, {
        "$query": {
            "$type": "Standard Material"
        },
        "Reflection/Roughness": 1
    })

c4d.EventAdd()

Thank you for reaching out to us. Your code looks very much like generated by a chatbot or generated with the help of a chatbot. Please note our Support Procedures: Scope of Support regrading the usage of AI. Please also post into the correct forum for future topics, I have moved your topic into the Cinema 4D SDK forum.

Your code does not make too much sense, I cannot dissect all the issues there. It is possible to do with the Nodes API what you want to do but it is more an API for experts. You can find here some code examples for it. Novice users should rather use graph descriptions which is a less powerful but also simpler API.

Cheers,
Ferdinand

To change the external thickness of each Contour node in a document, you could write something like using a graph description query:

"""Sets the external thickness of all 'Contour' nodes in Redshift material graphs of the active 
document to 2.
"""

import c4d
import maxon

doc: c4d.documents.BaseDocument  # The currently active document.
op: c4d.BaseObject | None  # The primary selected object in `doc`. Can be `None`.

def main() -> None:
    """Called by Cinema 4D when the script is being executed.
    """
    # Iterate over the material graphs of all Redshift materials in the document.
    for graph in maxon.GraphDescription.GetMaterialGraphs(
        doc, maxon.NodeSpaceIdentifiers.RedshiftMaterial):
        # Apply a graph description to each of them which ...
        maxon.GraphDescription.ApplyDescription(graph, 
        {
            # ... queries all nodes of type 'Contour' in the graph ...
            "$query": {
                "$qmode": maxon.GraphDescription.QUERY_FLAGS.MATCH_ALL | 
                          maxon.GraphDescription.QUERY_FLAGS.MATCH_MAYBE,
                "$type": "Contour",
            },
            # ... so that we can set the thickness value of all matching nodes to 2.
            "External/Thickness": 2
        })


if __name__ == '__main__':
    main()