[Tutor] Why super does not work !

[Karim]

On 01/17/2011 11:36 PM, Dave Angel wrote:
> On 01/-10/-28163 02:59 PM, Karim wrote:
>>
>>
>> Hello,
>>
>> I implemented Observer DP on a listbox (Tkinter) as follows and I don't
>> understand why super() is not working and Observable.__init__(self) is
>> working, cf below:
>>
>> class ListObservable(Listbox, Observable):
>> """Creation de widget Listbox"""
>> def __init__(self):
>> super(ListObservable, self).__init__()
>> #Observable.__init__(self)
>> self._value = None
>> self.listeContenu = StringVar()
>> self.listeContenu.set(' '.join(sorted(data_base.keys())))
>> self.liste = Listbox(listvariable=self.listeContenu, 
>> selectmode='single')
>> self.liste.grid(row=0, column=1, sticky=N+S+W)
>> self.liste.bind('<Button-1>', self.onSelect)
>>
>> _The error is:_
>> Traceback (most recent call last):
>> File "./observerAppliGraphique.py", line 118, in <module>
>> app=App()
>> File "./observerAppliGraphique.py", line 37, in __init__
>> self.sujet.attach(self.nom)
>> File "/home/karim/guiObserver/observable.py", line 11, in attach
>> self._observers.append(observer)
>> AttributeError: 'ListObservable' object has no attribute '_observers'
>>
>> And the Observable class is:
>>
>> class Observable(object):
>> """Sujet a observer"""
>> def __init__(self):
>> self._observers = []
>> print('constructeur observable')
>>
>> def attach(self, observer):
>> """Attache un nouvel observateur"""
>> self._observers.append(observer)
>>
>> def detach(self, observer):
>> """Retire un nouvel observateur"""
>> self._observers.remove(observer)
>>
>> def notify(self):
>> """Avertit tous les observateurs que l'observable change d'etat"""
>> for observer in self._observers:
>> observer.update()
>>
> Just looking at what you supply, I'd suppose that ListBox doesn't 
> correctly call super() in its own __init__() method.
>
> So I took a look at Tkinter.py, and sure enough, it just calls its own 
> direct parent, Widget.l
>
> super() only works if all the classes you use are done consistently.
>
> DaveA
>
Thanks for this precision!

Regards
Karim