[Tkinter-discuss] Creating a new widget class

[vtcodger]

I wonder if someone who understands Python and Tkinter a bit better than I
could help me out.  Basically, I'm trying to encapsulate the kind of messy
stuff associated with setting up a listbox with a scrollbar in a Python
class.  From my probably incredibly naive point of view, it doesn't look too
hard.

class ScrolledList(Frame,Listbox,Scrollbar) :
  #At this point we have a template for objects that have all the 
  #attributes and methods of Frames,Listboxes,and Scrollbars.  For 
  #names that occur in all, the Frame version takes precedence over 
  #the Listbox version and that in turn takes precedence over 
  #Scrollbar version

  def __init__ (self, Tkobject, height=4, width=50) :
    #This code is executed whenever a new scrolled list object is
    #created (instantiated)
    self.f = Frame(Tkobject)
    s = Scrollbar(self.f,orient=VERTICAL)
    self.l = Listbox(self.f, height=height, width=width,
yscrollcommand=s.set, exportselection=0)
   #We have now created a frame, scrollbar and listbox     

    s.config(command=self.l.yview) 
    s.pack(side=RIGHT, fill=Y); self.l.pack()
   #And configured the listbox and scrollbar to interact

And it creates a Tkinter object with a gazillion attributes.  Unfortunately
tk isn't one of them.  When I try to invoke the methods, I am informed that
the new object has no 'tk' attribute.  That's correct.  It doesn't. 
Apparently I have failed to call some necessary constructor.  But which?

Maybe I'm close to having it right because if I create a grid attribute in
the class and pass the parameters to the frame grid method, the scrolled
listbox can be configured and displayed.

  def grid(self,row=90,column=1,rowspan=5,columnspan=4,sticky=W) :
   
self.f.grid(row=row,column=column,rowspan=rowspan,columnspan=columnspan,sticky=sticky)

What am I doing wrong, or not doing right?
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