[Tutor] OOP help needed

Jim Byrnes jf_byrnes at comcast.net
Wed Jul 27 14:25:18 EDT 2016

On 07/27/2016 03:12 AM, Peter Otten wrote:
> Jim Byrnes wrote:
>> OOP has always driven me crazy.  I read the material and follow the
>> examples until I feel I understand them, but when I try to implement it
>> I end up with an error filled mess.
>> So I decided to give it another try.  When I got to the chapter on
>> tkinter I decided to solve all the exercises using OOP even though the
>> book solutions did not use OOP. The first one went fine:
> No, it didn't. The Goodbye.quit() method is missing the self argument and
> uses the inexistent self.window attribute.
> You don't see these bugs when you run the script because there is a global
> quit()... let's say function... that is called instead of the method.
> You can put a print() into Goodbye.quit() to verify the above.

OK right.  I ended up concentrating on exer2 when the problem was in 
exer1.  I should have known better than using quit() as a name.

>> #exer1.py
>> import tkinter
>> class Goodbye:
>>    def __init__(self):
>>      self.frame = tkinter.Frame(window)
>>      self.frame.pack()
>>      self.goodbye_button = tkinter.Button(self.frame, text='Goodbye',
>>        #command=quit)
>>        command=lambda: quit() )
> The lambda is superfluous -- command=quit will already invoke the global
> quit(). But what you actually intended is achieved with command=self.quit.
> self.quit is called "bound method".

Ok, thanks.

>>      self.goodbye_button.pack()
>>    def quit():
>        print("you'll never see this")
>>      self.window.destroy()
>> if __name__=='__main__':
>>    window = tkinter.Tk()
>>    myapp = Goodbye()
>>    window.mainloop()

Regards,  Jim

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