[Tutor] Recursive Tkinter buttons

[Michael Lange]

On Sat, 26 Feb 2005 19:48:25 +0000
Adam Cripps <kabads at gmail.com> wrote:

> On Fri, 25 Feb 2005 12:21:18 +0100, Michael Lange 
> <snip>
> > 
> > You see, in my example above I called the list "buttonlist" instead of "button"; maybe this naming
> > helps avoid confusion .
> > 
> > Best regards
> > 
> > Michael
> 
> Many thanks for the help here. 
> 
> I got all my buttons displayed and stored in the list with: 
> 
> for i in range (1, 11):
> 			submittext = ">>> "
> 			self.s = Button(text=submittext, command = self.showButton)
> 			self.s.grid(column=4, row=i+4)
> 			submitlist.append(self.s)
> 
Hi Adam,

note that there's no use in making the button an attribute of its parent class with

    self.s = Button(text=submittext, command = self.showButton)

because self.s gets overridden on every iteration in the for-loop; it's not a bug, but
might be a source of confusion, when you try to access self.s later in your code; you don't
need the reference anyway, because you keep the references to all buttons in the list.

> 
>  - however, when I click the button, I want self.showButton to know
> which one of them was pressed. I've seen in other gui programming the
> idea of an id or identifier - I can't see that here. Ideally, I would
> like to know the value of i in self.showButtons - but when I use
> self.showButtons(i) showButtons gets called straight at run time.
> 
> Any ideas? 

You have two options here:

1. use a lambda expression as button command, lambda allows you to pass an argument to the callback:

    s = Button(text=submittext, command = lambda index=i: self.showButton(index))

2. if you don't like lambdas, you can use the button's bind() method instead of the command option:

    s = Button(text=submittext)
    s.bind('<ButtonRelease-1>', self.showButton)
    s.bind('<KeyRelease-space>', self.showButton)

bind() passes an event to the callback which allows you to find out which widget sent the event via the
event's widget attribute:

    def showButton(self, event):
        button = event.widget
        print button['text']

I hope this helps

Michael