class AppProxy(object):
    def __init__(self, cpp_app_object):
        cpp_app_object.addProperty('App::PropertyFloat', 'testprop')

class VPProxy(object):
    def __init__(self, cpp_vp):
        cpp_vp.Proxy = self
        
    def attach(self, cpp_vp):
        self.cpp_app_object = cpp_vp.Object
        
    def updateData(self, cpp_app_object, propname):
        if propname == 'testprop':
            n = self.cpp_app_object.Name #fails if cpp_app_object was deleted

def make():
    cpp_app_object = App.ActiveDocument.addObject('App::FeaturePython')
    AppProxy(cpp_app_object)
    VPProxy(cpp_app_object.ViewObject)

doc = App.ActiveDocument
doc.undo(); doc.openTransaction('make'); make(); doc.commitTransaction()