How to change Tkinter label text on button press

问题:

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()

回答1:

Doing:

message = 'Button Pressed'

will not affect the label widget. All it will do is reassign the global variable message to a new value.

To change the label text, you can use its .config() method (also named .configure()):

def press():
    Instruction.config(text='Button Pressed')

---

In addition, you will need to call the pack method on a separate line when creating the label:

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

Otherwise, Instruction will be assigned to None because that is the method's return value.

回答2:

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')