NodeHandle

import maya.cmds as cmds
import maya.OpenMaya as om

class NodeHandle:
    def __init__(self,handle,weakReference=False):
        '''
            construct object by given name or MObject handle
            weakReference is an option to construct object as
            weak reference, enabling tracking if MObject handle is still valid within maya
        '''

        self.__weakReference = weakReference

        if isinstance(handle,(list,tuple)):
            handle = handle[0]

        if isinstance(handle, NodeHandle):
            handle = handle.handle()

        if not isinstance(handle, om.MObject):
            name = str(handle)
            handle = NodeHandle.getHandleByName(name)
            # handle to node was not created. possible problems?
            if handle is None:
                nodeNameTest = cmds.ls(name)
                if len(nodeNameTest)==0:
                    raise Exception,'node "%s" does not exist' % name
                if len(nodeNameTest)>1:
                    raise Exception,'there\'s more than one node "%s" in the scene' % name

        self.__handle = handle
        if self.__weakReference:
            self.__weakHandle = om.MObjectHandle(self.__handle)

        return

    def isWeakReference(self):
        'tests if we got support for weak reference methods (isAlive(), isValid()) for this node'

        return self.__weakReference

    def isAlive(self):
        'tests if handle to node is still alive (see MObjectHandle.isAlive() for more info)'
        if not self.isWeakReference():
            raise AssertionError,'operation not supported for non-weak references'
        return self.__weakHandle.isAlive()

    def isValid(self):
        'tests if handle to node is still valid (see MObjectHandle.isValid() for more info)'

        if not self.isWeakReference():
            raise AssertionError,'operation not supported for non-weak references'
        return self.__weakHandle.isValid()

    def __str__(self):
        'self cast to string: return full dag path for direct use with maya.cmds methods'
        return self.name()

    def __repr__(self):
        'representation for debugging: prints class name and node full path'
        return "%s(%s)" % (self.__class__.__name__,self.name())

    def handle(self):
        'returns MObject for this node'

        return self.__handle

    def path(self):
        dag = self.getDagFn()
        path = om.MDagPath();

        dag.getPath(path)
        return path

    def name(self):
        'returns full path version of node name'

        try:
            if not self.hasFn(om.MFn.kDagNode):
                return self.shortName()

            return self.path().fullPathName()
        except:
            return self.shortName()