import hou

def auto_select_on_display_flag_set(node, event_type, **kwargs):     # pylint: disable=W0613
    node.setSelected(node.isDisplayFlagSet())

def add_callback(kwargs):
    node = kwargs["node"]
    node.addEventCallback((hou.nodeEventType.FlagChanged,), auto_select_on_display_flag_set)

add_callback(kwargs)    # pylint: disable=E0602

reload(module)

from imp import reload

container = QtGui.QWindow.fromWinId(handle)
QWidget.createWindowContainer(container)

import hou

TEMP_NODE = "temp_wrangle_path"

def getCurrentNode(selected):
    selected = selected if selected else hou.selectedNodes()
    if not selected:
        print("Nothing selected!")
        return None

    input = selected[0].inputs()
    if not input:
        current = selected[0]
    else:
        current = input[0]
    return current

def createCenterPointsNode(selected=None):
    current = getCurrentNode(selected)
    if not current:
        return None

    aw = current.createOutputNode("attribwrangle", "__temp_prim_center_snap_helper__")
    aw.setTemplateFlag(1)   # tempalte flag for snapping
    aw.parm("class").set(1)
    aw.parm("snippet").set("addpoint(0, v@P);") # create center points
    aw.setComment("helper node for snapping to primitive centers")
    aw.setGenericFlag(hou.nodeFlag.DisplayComment, 1)
    
    context = current.parent()  # context
    context.setUserData(TEMP_NODE, aw.path())  # store path to the temporary wrangle
    return aw

def removeHelperNode(selected=None):
    current = getCurrentNode(selected)
    if not current:
        return

    context = current.parent()  # context
    aw = hou.node(context.userData(TEMP_NODE))
    aw.destroy()    # delete node
    context.destroyUserData(TEMP_NODE)

# usage:
createCenterPointsNode() # create helper
removeHelperNode() # remove helper

strictparsing: false