Duplication smells

Duplication. A programmer's worst nightmare. Does that sound over the top? Maybe it does, but I guess most programmers would agree that duplication is one of the worst code smells around. So, a programmer should do everything to prevent and reduce duplication, right? Well, I think that in the case of simple duplication we all agree on that. With simple I mean that two pieces of code are textually equal or very similar, e.g.:

patterns.Publisher().registerObserver(self.onMatchAllChanged,
   eventType='view.taskcategoryfiltermatchall')
patterns.Publisher().registerObserver(self.onFilteredCategoriesChanged,
   eventType='view.taskcategoryfilterlist')
patterns.Publisher().registerObserver(self.onAddCategoryToTask,
   eventType='task.category.add')
patterns.Publisher().registerObserver(self.onRemoveCategoryFromTask,
   eventType='task.category.remove')

This is actual code from Task Coach (blush) and represents a component registering itself as observer for different event types. Of course, this type of duplication is rather easy to fix, e.g.:

callbacks = {'view.taskcategoryfiltermatchall': self.onMatchAllChanged, ...}
publisher = patterns.Publisher()
for eventType, callback in callbacks.items():
   publisher.registerObserver(callback, eventType)

But then there's also duplication that's not strictly textual, but more structural. For example, two for-loops looping over the same datastructure but with a different body. An example from Task Coach again. These two event handlers update a check-listbox (a list with items that can be checked and unchecked by the user) when categories are added to or removed from a task:

def onAddCategoryToTask(self, event):
   for category in event.values():
       if self._checkListBox.FindString(category) == wx.NOT_FOUND:
           self._checkListBox.Append(category)
   self.Enable(len(self.__taskList.categories()) > 0)

def onRemoveCategoryFromTask(self, event):
   for category in event.values():
       if category not in self.__taskList.categories():
           self._checkListBox.Delete(self._checkListBox.FindString(category))
   self.Enable(len(self.__taskList.categories()) > 0)

Removing this type of duplication is more tricky. Refactoring to something like the following should work (untested):

def updateCategoriesListbox(self, categories, updateNeeded, updateListbox):
   for category in categories:
       if updateNeeded(category):
           updateListbox(category)
   self.Enable(len(self.__taskList.categories()) > 0)

def onAddCategoryToTask(self, event):
   def updateNeeded(category):
       return self._checkListBox.FindString(category) == wx.NOT_FOUND

   def updateListbox(category):
       self._checkListBox.Append(category)

   self.updateCategoriesListbox(event.values(), updateNeeded, updateListbox)

def onRemoveCategoryFromTask(self, event):
   def updateNeeded(category):
       return category not in self.__taskList.categories()

   def updateListbox(category):
       self._checkListBox.Delete(self._checkListBox.FindString(category))

   self.updateCategoriesListbox(event.values(), updateNeeded, updateListbox)

But this raises the question: is the increase in lines of code and number of functions worth the reduction of duplication? Or did I miss a more simple solution?