Mailing List Archive: Tkinter and classes

Tkinter and classes

Aug 22, 1999, 10:34 AM

Post #1 of 3 (255 views)

Hi all. I'm just fiddling about with Tkinter buttons and labels trying
to get the text in a Label to change when I press a button, this is
essentially what I've done:

class Helloworld:
def __init__(self, master):
_lblstr = StringVar()
_lblstr.set("hello world")

frm = Frame(master)
frm.pack()

but = Button(frm, text='Hello!', command=setLabel)
but.grid(row=0)

lbl = Label(frm, textvariable=_lblstr)
lbl.grid(row=1)

def setLabel(self):
_lblstr.set("HELLO WORLD!!")

This will run, but barfs out on the callback.
Am I misunderstanding the relationship between the callback to the
namespace of the class?

Thanks!

Justin

Tkinter and classes [ In reply to ]

frankn=news at cs

Aug 23, 1999, 12:37 AM

Post #2 of 3 (256 views)

Permalink

Justin Muir <jkmuir@uniserve.com> wrote:

> class Helloworld:
> def __init__(self, master):
> _lblstr = StringVar()
> _lblstr.set("hello world")

> frm = Frame(master)
> frm.pack()

> but = Button(frm, text='Hello!', command=setLabel)
> but.grid(row=0)

> lbl = Label(frm, textvariable=_lblstr)
> lbl.grid(row=1)

> def setLabel(self):
> _lblstr.set("HELLO WORLD!!")

> This will run, but barfs out on the callback.
> Am I misunderstanding the relationship between the callback to the
> namespace of the class?

Try replacing _lblstr by self._lblstr to make it an instance variable.

As you programmed it above _lblstr is just local to the __init__ function
and disappears as soon as the function is finished. So setLabel doesn't
know anything about a _lblstr.

Cheers, Frank

--
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Tkinter and classes [ In reply to ]

jkmuir at uniserve

Aug 23, 1999, 2:27 PM

Post #3 of 3 (254 views)

Permalink

Thanks for the responses! They were timely and informative.

Again, thank you !

Justin.