Hi,
Thank you all for you responses. With Stewart's answer I could get it
working. Those were my first lines in python (that is why I had so many
semi-colons - I'm so used to C and C++).
And also thanks for the explanation. One really needs to know how the
programming language works when writing a program.
Cheers,
Dídac
[EMAIL PROTECTED] wrote:
> Hello Dídac,
>
> just to add an explanation, why your code doesn't work:
>
> >from Tkinter import *
>
>> root = Tk();
>>
>> def cb(x):
>> print x;
>>
>
>
>> for i in range(5):
>> b = Button(root,text=i,command=lambda:cb(i));
>>
>
> The part "lambda:cb(i)" is a function which gets evaluated
> (called) when a button is clicked. It is evaluated
> in the scope where it is defined. In this scope (the global scope)
> the for-loop has finished running long ago.
> Thus 'i' is always evaluated to '4' regardless which
> button is pressed because this is the value of 'i'
> after the end of the loop.
>
> Stewart's code:
> b = Button(root,text=i,command=lambda i=i:cb(i));
> This code works because it turns the loop variable 'i'
> into a default value for the parameter 'i' of the lambda function.
> And default values are evaluated when the function is defined,
> i.e. while the loop is running.
>
>
>> b.pack();
>>
>> root.mainloop();
>>
>
> Hope this helps to demystify this behaviour,
>
> Matthias Kievernagel
> (mkiever/at/web/dot/de)
> _______________________________________________
> Tkinter-discuss mailing list
> [email protected]
> http://mail.python.org/mailman/listinfo/tkinter-discuss
>
>
>
--
------------------------------------------------------------------------
*Dídac Busquets i Font*
Investigador Ramón y Cajal
Universitat de Girona
Dept. d'Electrònica, Informàtica i Automàtica
Institut d'Informàtica i Aplicacions
Edifici P-IV, Despatx 128
Campus Montilivi
17071 Girona
Tel. (+34) 972.41.81.79
Fax. (+34) 972.41.80.98
e-mail: [EMAIL PROTECTED]
web: http://eia.udg.es/~busquets
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Abans d'imprimir aquest correu electrònic pensa si és necessari fer-ho:
el medi ambient és cosa de tots.
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