How to change Tkinter label text on button press

Question

I have this code, and its meant to change the text of the Instruction label when the item button is pressed. It doesn't for some reason, and I'm not entirely sure why. I've tried creating another button in the press() function with the same names and parameters except a different text.

import tkinter
import Theme
import Info

Tk = tkinter.Tk()
message = 'Not pressed.'

#Sets window Options
Tk.wm_title(Info.Title)
Tk.resizable(width='FALSE', height='FALSE')
Tk.wm_geometry("%dx%d%+d%+d" % (720, 480, 0, 0))


#Method run by item button
def press():
    message = 'Button Pressed'
    Tk.update()

#item button
item = tkinter.Button(Tk, command=press).pack()

#label
Instruction = tkinter.Label(Tk, text=message, bg=Theme.GUI_hl2, font='size, 20').pack()

#Background
Tk.configure(background=Theme.GUI_bg)
Tk.mainloop()

Solution

You can make message a StringVar to make callback.

message = tkinter.StringVar()

message.set('Not pressed.')

You need to set message to be a textvariable for Instruction:

Instruction = tkinter.Label(Tk, textvariable=message, font='size, 20').pack()

and then

def press():
    message.set('Button Pressed')

Comments

[Phoenix]

PY_VAR0 has replaced the "Button Not Pressed" and "Button Pressed" text it would seem

[fdsa]

@Phoenix don't understand your comment

[Phoenix]

When I run my program, It displays "PY_VAR0" Instead of "Button Pressed", which should be displayed after it is pressed, or "Not Pressed" before it is pressed.

[Pyd]

AttributeError: 'NoneType' object has no attribute '_root'