[Tutor] Why super does not work !

[Dave Angel]

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