带有tkinter的python3：从函数调用小部件

Question

I'm having a problem with this code:

from tkinter import *

class app:
    def create(arrSettings):
            proot = Toplevel()
            proot.title("Settings")

            m = Frame(proot).pack()    #Some Frames so I can arrange them how I'd like to
            mcan = Canvas(proot)
            mcan.pack(fill="both", side="left")

            x = Frame(proot).pack()
            xcan = Canvas(proot)
            xcan.pack(fill="both", expand="yes", side="left")

            win_0 = Frame(xcan)
            lbl_0 = Label(win_0, text="Option0").pack()
            txt_0 = Text(win_0).pack()
            win_0.pack()

            win_1 = Frame(xcan)
            lbl_1 = Label(win_1, text="Option1").pack()
            txt_1 = Text(win_1).pack()
            win_1.pack()


            btn_menu0 = Button(mcan, text="Menu0", command=app.func_btn_menu0).pack()
            btn_menu1 = Button(mcan, text="Menu1", command=app.func_btn_menu1).pack()


    def func_btn_menu0():
            lbl_0.config(text="foo")     # <-- Problem
            txt_0.insert("end", "bar")   # <-- Problem

    def func_btn_menu1():
            pass

(I left the code for the design(bg, border, ...) out)

This is another window which will be started by the main one. It shows some buttons on the left and some labels and textboxes on the right.

Whenever a button on the left has been pushed the text of the labels should be changed.

That's the problem: When I push a button I get this error and the text won't be changed:

Exception in Tkinter callback
Traceback (most recent call last):
File "/usr/lib/python3.4/tkinter/__init__.py", line 1536, in __call__
return self.func(*args)
File "/[...]/program.py", line 27, in colormain
lbl_0.config(text="Background")
NameError: name 'lbl_0' is not defined

I don't really understand why this gives me an error so I'd like to ask you.

This code is being started from the main window with the code:

program.app.create(arrSettings) #arrSettings is an array in which some colors for the design are

Thanks in advance.

Answer 1

Do not declare and pack in the same line

Return of this peice of code is None

Label(win_0, text="Option0").pack()

whereas, this returns an object of Label class

Label(win_0, text="Option0")

so use:-

lbl_0 = Label(win_0, text="Option0")
lbl_0.pack()

instead of

lbl_0 = Label(win_0, text="Option0").pack()

Also use self object as argument to functions. Check that the variables are in scope wherever you are using it. This should help you get through this error...