Nuke Python get knob value for if statement

Question

I am relatively new to Python and I need some help. This is also my first post on this site. I am trying to change the value of the colorspace knob in Read Node I have labeled "Plate". I would like to use that value later on. Here is my code so far:

def LabelPlate():
    n = nuke.thisNode()
    if n != None:
        label = n['label'].value()
        n['label'].setValue('Plate')


def LabelLook():
    name= "Plate"
    for node in nuke.allNodes():
        if name == node.knob("label").value():
            return True

def LabelLookTwo():
    name= "Plate"
    for node in nuke.allNodes():
        if name == node.knob("label").value():
            return node.knob("name").value()


def PlateColorspaceSet():
    n = LabelLookTwo()
    if nuke.toNode("n")["colorspace"].value() == "default (sRGB)":
        nuke.toNode("n")["colorspace"].setValue("sRGB")

def LabelQuestion():
    if LabelLook() != True:
        if nuke.ask('Is this Read your main Plate?'):
            LabelPlate()
            PlateColorspaceSet()


nuke.addOnUserCreate(LabelQuestion, nodeClass = 'Read')

So order of events:

1. Bring in Read node

2. Ask if Read node is your main plate

   a. If yes, label node as "Plate", proceed to step 3
   b. If no, bring in unlabeled Read node

3. Change colorspace in node labeled "Plate" from default to an actual value.

So far, I can get the first 2 steps to work. But on step 3, I get

"'NoneType' object has no attribute 'getitem'"

Any ideas why? Is there a better way to get the colorspace value?

Answer 1

I figured out the problem.

nuke.addOnUserCreate is where I was calling the function on the creation of the read node. Problem is, it runs the script before everything exists. So not everything works because not everything is there in Nuke yet, so things, like my variable n = LabelLookTwo(), return as None.

Using addOnCreate instead runs the script after the node and it's defaults have been set and created. So using this, the rest of the script runs exactly as originally written.

Where I found the answer