Make Null

import hou


def main(nodes=None):
    # First we make sure we are in an approved category by checking
    # against one of the selected nodes
    if not nodes:
        if hou.selectedNodes():
            nodes = hou.selectedNodes()
        else:
            msg = "Please select some nodes"
            exitWithStatusMessage(msg)
    if not isinstance(nodes, (list, tuple)):
        nodes = [nodes]
    curCategory = nodes[0].type().category().name()

    approvedCategories = [
        'Sop', 'Driver', 'Vop', 'Cop2', 'Chop', 'Object', 'Dop']
    color = hou.Color([0, 0, 0])

    if curCategory in approvedCategories:
        name = "out"
        for aNode in nodes:
            # If we are in the vop category we want to name and place it
            # differently since vops go left to right not top to bottom
            if curCategory == "Vop":
                name = "n_{0}".format(aNode.name())
                xPos = aNode.position()[0] + 2
                yPos = aNode.position()[1]
            else:
                if curCategory == "Object":
                    name = "null"
                else:
                    # If the selected node has a unique name, use it for our
                    # new null. If it's a ray, points from volume, or copy node
                    # name the null vis so we can view without the obnoxious
                    # mandatory geo template. If it has a default name just
                    # name it OUT. If the parent node has render in the name,
                    # name the null render. If iso is in the name, its
                    # probably a blast node so strip iso and name itn the rest
                    if "render" in aNode.parent().name().lower():
                        name = "Render"
                    elif aNode.type().name() == "serialize":
                        if aNode.parm("operation").eval() == 1:
                            name = aNode.parm("output").evalAsString()
                        else:
                            name = "OUT_{0}".format(aNode.name())
                    elif ("ray" in aNode.type().name() or
                            "copy" in aNode.type().name() or
                            "pointsfromvolume" in aNode.type().name()):
                        name = "vis_{0}".format(aNode.name())
                        color = hou.Color([0.306, 0.306, 0.306])
                    elif aNode.type().name() in aNode.name():
                        name = "OUT"
                    elif 'iso' in aNode.name():
                        name = 'OUT_{0}'.format(
                            "_".join(aNode.name().split("_")[1:]))
                    elif 'object_merge' in aNode.type().name():
                        if 'IN_' in aNode.name():
                            name = aNode.name()[3:]
                    else:
                        name = "OUT_{0}".format(aNode.name())
                xPos = aNode.position()[0]
                yPos = aNode.position()[1] - 1

            if(aNode.parent().type().name() in
               ["subnet", "sopsolver", "dopnet"]):
                null = aNode.parent().createNode('output', name)
                if aNode.parent().type().name() != "dopnet":
                    numoutputs = -1
                    for n in aNode.parent().children():
                        if n.type().name() == "output" and n != null:
                            numoutputs = max(numoutputs,
                                             n.parm('outputidx').eval())
                            print n.path()
                    null.parm('outputidx').set(numoutputs+1)
            else:
                null = aNode.parent().createNode("null", name)
            null.setPosition(hou.Vector2(xPos, yPos))

            # If we are in sops or dops then we can set the display flags
            if curCategory == "Sop" or curCategory == "Dop":
                null.setDisplayFlag(True)
                if curCategory == "Sop":
                    null.setRenderFlag(True)
            null.setColor(color)
            null.setCurrent(True, clear_all_selected=True)
            # Now we set the inputs. If something goes wrong though we will
            # just give up and delete the node. This happens if a node with no
            # outputs is in the selection ie. rop node or chopnet
            try:
                # For all the outputs in a node, go to each. Loop through all
                # of that nodes inputs until we have found the original node.
                # We now know the proper index and can set the inputs correctly
                for outputs in aNode.outputs():
                    i = 0
                    for inputs in outputs.inputs():
                        if inputs is not None:
                            if aNode.name() == inputs.name():
                                outputs.setInput(i, null)
                            else:
                                i += 1
                null.setFirstInput(aNode)
            except:
                null.destroy()
    return null


def exitWithStatusMessage(msg):
    hou.ui.setStatusMessage(msg)
    exit()