How to replace the text with the previous text in the label?

I am trying to write a code to have a label, and a button, and whenever we click on the button the defined text just replaces with the previous text in the Label. Right now it adds it the previous text.

from tkinter import *

root = Tk()
root.geometry("400x400")

my_label = Label(text="Hello").pack()

def test():
    my_label = Label(text="Bye").pack()

my_button = Button(root, text="Open a file", command=test).pack()

root.mainloop()

I saw that people using config to do that. But I don’t understand what is the problem with my code.

from tkinter import *

root = Tk()
root.geometry("400x400")

global my_label
my_label = Label(text="Hello").pack()

def test():
    my_label.config(text="Bye")


my_button = Button(root, text="Open a file", command=test).pack()

root.mainloop()

It gives me this error:

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

>Solution :

You don’t use global at the global level. You should remove that.

The PROBLEM is that the .pack() method returns None. Tkinter is a hopelessly antiquated relic of software days gone by, and does not use good object practices. You need

my_label = Label(text="hello")
my_label.pack()