[Tkinter-discuss] Can't do proper event binding in a for loop
thea_t
siatogia at yahoo.com
Tue Oct 19 23:18:51 CEST 2010
Very clever! Thanks!
Mick O'Donnell wrote:
>
> Much simpler, and closer to the original posters intention.
> Replace your up_and_down function with:
>
> def up_and_down(*buttons):
>
> for i in range(len(buttons)-1):
> buttons[i].bind("<Down>", lambda e, x=buttons[i+1]: x.focus_set())
>
> for i in range(1, len(buttons)):
> buttons[i].bind("<Up>", lambda e, x=buttons[i-1]: x.focus_set())
>
>
> ...basically, with this code, the "i" is being evaluated within the loop,
> and passed to the lambda as the x parameter. The 'e' parameter
> will be set to the event object.
>
> Mick
>
>
> On Tue, Oct 19, 2010 at 2:01 PM, thea_t <siatogia at yahoo.com> wrote:
>>
>> Thank you guys! I know what's wrong now! :)
>>
>>
>>
>> Michael Lange wrote:
>>>
>>> Hi,
>>>
>>> Thus spoketh Firat Ozgul <ozgulfirat at gmail.com>
>>> unto us on Tue, 19 Oct 2010 13:19:03 +0300:
>>>
>>>> Hello,
>>>>
>>>> for loop doesn't work, because in a for loop all events will be bound
>>>> all at once, and you will only see the effect of the last binding. You
>>>> need something that binds events one by one.
>>>>
>>>> If I were you, I would use the next() method of Python iterators:
>>>
>>> I think the OP suffered from a different problem in her code, namely the
>>> IndexError that will be raised when i+1 or i-1 become >2 or <0 .
>>> I guess what she wanted to achieve can be done, but not with this simple
>>> lambda, she needs to catch the IndexError with something like:
>>>
>>> def up_and_down(*buttons):
>>>
>>> def callback(event):
>>> index = list(buttons).index(event.widget)
>>> try:
>>> if event.keysym == 'Up':
>>> buttons[index - 1].focus_set()
>>> elif event.keysym == 'Down':
>>> buttons[index + 1].focus_set()
>>> except IndexError:
>>> pass
>>>
>>> for i in range(len(buttons)-1):
>>> buttons[i].bind("<Down>", callback)
>>>
>>> for i in range(1, len(buttons)):
>>> buttons[i].bind("<Up>", callback)
>>>
>>> I hope this helps
>>>
>>> Michael
>>>
>>> .-.. .. ...- . .-.. --- -. --. .- -. -.. .--. .-. --- ... .--. .
>>> .-.
>>>
>>> Wait! You have not been prepared!
>>> -- Mr. Atoz, "Tomorrow is Yesterday", stardate 3113.2
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>>
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