That does it!, thanks.
Thinking about it, when I created a derived class with an __init__
method, I overrode the base class's init. It should have been
intuitive that I needed to explicitly call baseclass.__init(self), it
wasn't. It might have hit me if the fault was related to someting in
baseclass.__init() not taking place, but the recursion loop didn't give
me a clue. Any idea why failing to init the base class caused the loop?
Bill
Christopher Subich wrote:
> William Gill wrote:
>
>> O.K. I tried from scratch, and the following snippet produces an
>> infinite loop saying:
>>
>> File "C:\Python24\lib\lib-tk\Tkinter.py", line 1647, in __getattr__
>> return getattr(self.tk, attr)
>>
>> If I comment out the __init__ method, I get the titled window, and
>> print out self.var ('1')
>>
>>
>> import os
>> from Tkinter import *
>>
>> class MyApp(Tk):
>> var=1
>> def __init__(self):
>> pass
>> def getval(self):
>> return self.var
>>
>>
>> app = MyApp()
>>
>> app.title("An App")
>> print app.getval()
>> app.mainloop()
>
>
> You're not calling the parent's __init__ inside your derived class. I
> would point out where the Python Tutorial points out that you should do
> this, but it's not in the obvious place (Classes: Inheritance).
>
> Python does -not- automagically call parent-class __init__s for derived
> classes, you must do that explicitly. Changing the definition of your
> class to the following works:
> >>> class MyApp(Tk):
> var=1
> def __init__(self):
> Tk.__init__(self)
> pass
> def getval(self):
> return self.var
>
> It works when you comment out __init__ because of a quirk in Python's
> name resolution. As you'd logically expect, if you don't define a
> function in a derived class but call it (such as instance.method()), it
> will call the method from the base class.
>
> You just proved that this works for __init__ methods also. When you
> didn't define __init__ for your derived class, MyApp() called
> Tk.__init__(), which Does the Right Thing in terms of setting up all the
> specific Tkinter-specific members.
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