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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: Bind event is giving me a bug.
Date: Wed, 15 Jan 2014 20:44:32 -0500
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On 1/15/2014 3:16 PM, eneskristo@gmail.com wrote:
> While working with tkinter in python 3.3, I had the following problem.

Please paste working code that people can experiment with.

from tkinter import *

> def get_text(event):

If this were a method, (which the indent of the body suggests it once 
was) it would have to have a 'self' parameter, and you would have to 
bind a bound method.

>              self.number_of_competitors = entered_text.get()

Since it is just a function, and has no 'self' parameter, this raises 
NameError. I condensed the function to

             try:
                 int(entered_text.get())
                 root.destroy()
             except ValueError:
                 label.config(text = "Enter the number of competitors. 
Please enter a number.")

>              try:
>                  self.number_of_competitors = int(self.number_of_competitors)
>              except:

Bare excepts are bad.

>                  pass
>              if type(self.number_of_competitors) == int:
>                  root.destroy()
>              else:
>                  label.config(text = "Enter the number of competitors. Please enter a number.")
> root = Tk()
> label = Label(root, text = "Enter the number of competitors.")
> label.pack(side = TOP)
> entered_text = Entry(root)

Since Entry only allows one line, I would have thought that it should 
take a command=func option invoked by \n. Instead, it seems to swallow 
newlines.

> entered_text.pack()
> Button(root, text = "Submit", command = get_text).pack()

As near as I can tell, the Button button-press event in *not* bound to 
get_text but to a fixed event handler that calls get_text *without* an 
argument.

> root.bind('<Enter>', get_text)

This does bind to an event so that it does call with an event arg. I 
just removed this and the window acts as it should.

Since get_event ignores event, event=None should make it work either 
way. However, when I try that, the window disappears without being 
touched, as if \n is randomly generated internally. So I would say to 
skip this until you know more than I do.

> root.mainloop()
>
> This is a buggy part of the code. When I run it, instead of doing what it should do, it responds to all events BUT enter. I'm not sure if this error is on tkinters or my side. Please help!

-- 
Terry Jan Reedy