在Python 3中使用tkinter时，如何在每次按下函数时获得一个按钮来运行函数？

Question

import tkinter as tk
panel = tk.Tk()
num = 42
lbl1 = tk.Label(panel, text = str(num))

Let's say I have a function and button like this:

def increase():
    lbl1.configure(text = str(num+1))

btn = tk.Button(panel, text = 'Increase', command = increase)

panel.mainloop()

This button will make the number that is the label increase by 1 when pressing the button. However, this only works once before the button does absolutely nothing. How can I make it so that every time I press the button, the number increases by 1?

Answer 1

You never saved the incremented value of num .

def increase():
    global num # declare it a global so we can modify it
    num += 1 # modify it
    lbl1.configure(text = str(num)) # use it

Answer 2

It's because num is always 43

import tkinter as tk
num = 42

def increase():
    global num
    num += 1
    lbl1.configure(text = str(num))


panel = tk.Tk()

lbl1 = tk.Label(panel, text = str(num))
lbl1.pack()
btn = tk.Button(panel, text = 'Increase', command = increase)
btn.pack()
panel.mainloop()