Instances Read & Camera nodes in Nuke, so you don't have to risk cloning and corrupting your script.

nodeInstancer.py

# Don't forget to add "import nodeInstancer" in your menu.py

import nuke

def readInstancer():

    # Save original node type to variable and deselect, so that multiple new instances don't daisy chain upon creation.
    originalNode = nuke.selectedNode()
    originalNodeClass = originalNode.Class()
    originalNode['selected'].setValue(0)
    origXpos = originalNode['xpos'].value()
    origYpos = originalNode['ypos'].value()
    
    # Create Postage Stamp
    nodeInstance = nuke.createNode('PostageStamp')


    # Hook up the input of our instance to the original node
    nodeInstance.setInput(0, originalNode)

    # Set instance name & node colour, then hide it's input
    nodeInstance['tile_color'].setValue(int('%02x%02x%02x%02x' % (50, 50, 50, 1), 16))
    nodeInstance.setName(originalNode['name'].value() + " INSTANCE")
    nodeInstance['hide_input'].setValue(1)

    # Force instance position to be below + off to the right a tad for clear visibility
    nodeInstance['xpos'].setValue(origXpos + 100)
    nodeInstance['ypos'].setValue(origYpos + 150)

    # If it doesn't already exist, create new tab, then create a disabled file knob that shows the original file path. At IE, this will be blank for Cameras.
    nodeInstance.addKnob(nuke.Tab_Knob('InstanceTab', "Instance"))
    nodeInstance.addKnob(nuke.File_Knob('origFile', "Original File"))
    nodeInstance['origFile'].setValue(originalNode['file'].value())
    nodeInstance['origFile'].setEnabled(False)

    # Create Python script button, that jumps to the original.
    nodeInstance.addKnob(nuke.PyScript_Knob('showOriginal', "Show Original Node", "origNode = nuke.thisNode().input(0)\norigXpos = origNode.xpos()\norigYpos = origNode.ypos()\nnuke.zoom(2, [origXpos,origYpos])\nnuke.thisNode()['selected'].setValue(False)\norigNode['selected'].setValue(True)\nnuke.show(origNode)"))
    nodeInstance['showOriginal'].setFlag(0x1000)


    # If it doesn't already exist, add instance tab to the original node
    if originalNode.knob('InstanceTabOrig'):
        return
    else:    
        originalNode.addKnob(nuke.Tab_Knob('InstanceTabOrig', "Instance"))

        # Add buttons to original node to show/hide viewer inputs, and de-instance everything.
        originalNode.addKnob(nuke.PyScript_Knob('showHideInputs', "Show / Hide Hidden Inputs", "n = nuke.thisNode()\nchildren = n.dependent(nuke.INPUTS | nuke.HIDDEN_INPUTS)\nallinstances = []\n\nfor i in children:\n    if i.Class() =='PostageStamp' or i.Class() == 'Scene':\n        allinstances.append(i)\n\nfor x in allinstances:\n    if x['hide_input'].value() == 1:\n        x['hide_input'].setValue(0)\n    else:\n        x['hide_input'].setValue(1)"))

        originalNode.addKnob(nuke.PyScript_Knob('deinstanceNodes', "De-Instance Connected Nodes", "import nuke\n\ndef duplicate_node(node, to_file = None):\n\n    orig_selection = nuke.selectedNodes()\n\n    [n.setSelected(False) for n in nuke.selectedNodes()]\n    node.setSelected(True)\n\n    if to_file is not None:\n        nuke.nodeCopy(to_file)\n        [n.setSelected(False) for n in orig_selection]\n        return\n\n\n    nuke.nodeCopy('%clipboard%')\n    node.setSelected(False)\n\n    if to_file is None:\n        nuke.nodePaste('%clipboard%')\n        new_node = nuke.selectedNode()\n    [n.setSelected(False) for n in nuke.selectedNodes()]\n    [n.setSelected(True) for n in orig_selection]\n\n    return new_node\n\n\n\n\n\n\n\n\n\nn = nuke.thisNode()\nchildren = n.dependent(nuke.INPUTS | nuke.HIDDEN_INPUTS)\nallinstances = []\n\nfor i in children:\n    if i.Class() == 'PostageStamp' or i.Class() == 'Camera2':\n        allinstances.append(i)\n\nn.removeKnob(n.knobs()['showHideInputs'])\nn.removeKnob(n.knobs()['deinstanceNodes'])\nn.removeKnob(n.knobs()['InstanceTabOrig'])\n\nfor x in allinstances:\n    instanceChildren = x.dependent(nuke.INPUTS | nuke.HIDDEN_INPUTS)\n    instanceChildrenList = []\n\n    newNode = duplicate_node(n)\n    newNode['xpos'].setValue(x['xpos'].value())\n    newNode['ypos'].setValue(x['ypos'].value())\n\n    for g in instanceChildren:\n        instanceChildrenList.append(g)\n\n    for k in instanceChildrenList:\n        k.setInput(0, newNode)\n\n    nuke.delete(x)\n\nnuke.message(str(len(allinstances))+' instances converted to their original nodes')"))
        
        
        
        
        
def cameraInstancer():
  
    # Save original node type to variable and deselect, so that multiple new instances don't daisy chain upon creation.
    originalNode = nuke.selectedNode()
    originalNodeClass = originalNode.Class()
    originalNode['selected'].setValue(0)
    origXpos = originalNode['xpos'].value()
    origYpos = originalNode['ypos'].value()
    
    # Create Postage Stamp
    nodeInstance = nuke.createNode('Camera2')
    
    # Expression-link knobs
    originalNodeName = originalNode.name()
    for j in nodeInstance.knobs():
        nodeInstance[j].setExpression( originalNodeName + '.' + j )
    nodeInstance['xpos'].setExpression('')
    nodeInstance['ypos'].setExpression('')
    nodeInstance['selected'].setExpression('')
    nodeInstance['tile_color'].setExpression('')


    # Set instance name & node colour
    nodeInstance['tile_color'].setValue(int('%02x%02x%02x%02x' % (50, 50, 50, 1), 16))
    nodeInstance.setName(originalNode['name'].value() + " INSTANCE")

    # Force instance position to be below + off to the right a tad for clear visibility
    nodeInstance['xpos'].setValue(origXpos + 100)
    nodeInstance['ypos'].setValue(origYpos + 150)

    # If it doesn't already exist, create new tab.
    nodeInstance.addKnob(nuke.Tab_Knob('InstanceTab', "Instance"))

    # Create Python script button, that jumps to the original.
    nodeInstance.addKnob(nuke.PyScript_Knob('showOriginal', "Show Original Node", "origNode = nuke.thisNode().dependencies(1)[0]\norigXpos = origNode.xpos()\norigYpos = origNode.ypos()\nnuke.zoom(2, [origXpos,origYpos])\nnuke.thisNode()['selected'].setValue(False)\norigNode['selected'].setValue(True)\nnuke.show(origNode)"))
    nodeInstance['showOriginal'].setFlag(0x1000)


    # If it doesn't already exist, add instance tab to the original node
    if originalNode.knob('InstanceTabOrig'):
        return
    else:    
        originalNode.addKnob(nuke.Tab_Knob('InstanceTabOrig', "Instance"))

        # Add button to original node to de-instance everything.
        originalNode.addKnob(nuke.PyScript_Knob('deinstanceNodes', "De-Instance Connected Nodes", "import nuke\n\ndef duplicate_node(node, to_file = None):\n\n    orig_selection = nuke.selectedNodes()\n\n    [n.setSelected(False) for n in nuke.selectedNodes()]\n    node.setSelected(True)\n\n    if to_file is not None:\n        nuke.nodeCopy(to_file)\n        [n.setSelected(False) for n in orig_selection]\n        return\n\n\n    nuke.nodeCopy('%clipboard%')\n    node.setSelected(False)\n\n    if to_file is None:\n        nuke.nodePaste('%clipboard%')\n        new_node = nuke.selectedNode()\n    [n.setSelected(False) for n in nuke.selectedNodes()]\n    [n.setSelected(True) for n in orig_selection]\n\n    return new_node\n\n\n\n\n\n\n\n\n\nn = nuke.thisNode()\nchildren = n.dependent(nuke.EXPRESSIONS)\nallinstances = []\n\nfor i in children:\n    if i.Class() == 'Camera2':\n        allinstances.append(i)\n\nn.removeKnob(n.knobs()['deinstanceNodes'])\nn.removeKnob(n.knobs()['InstanceTabOrig'])\n\nfor x in allinstances:\n    instanceChildren = x.dependent(nuke.EXPRESSIONS)\n    instanceChildrenList = []\n\n    newNode = duplicate_node(n)\n    newNode['xpos'].setValue(x['xpos'].value())\n    newNode['ypos'].setValue(x['ypos'].value())\n\n    for g in instanceChildren:\n        instanceChildrenList.append(g)\n\n    for k in instanceChildrenList:\n        k.setInput(0, newNode)\n\n    nuke.delete(x)\n\nnuke.message(str(len(allinstances))+' instances converted to their original nodes')"))
    
    
    
    
    
def nodeInstancer():
  
    originalNode = nuke.selectedNode()
    originalNodeClass = originalNode.Class()
    
    # If the selected node is a Read node, create a Read instance.
    if originalNodeClass == 'Read':
        readInstancer()
	
    # If the selected node is a Camera, and not an instance of another Camera, we want to create a camera instance.
    elif originalNodeClass == 'Camera2' and originalNode['tile_color'].value() != (int('%02x%02x%02x%02x' % (50, 50, 50, 1), 16)):
        cameraInstancer()
    
    # If the selected node isn't a Read or Camera node, throw up an error message.
    else:
        nuke.message("Only Read and Camera nodes may be instanced.")
        

# Add a menu item under the Edit menu, and assign meta+i as the hotkey 
nuke.menu("Nuke").addCommand("Edit/Node Instancer", 'nodeInstancer()', 'meta+i')