Set button command to None but no effect in python tkinter

I want to remove button's click event when click it, but this code has no effect. Every button popup msgbox again and again:

from tkinter import *
from tkinter import messagebox

root = Tk()
root.geometry("500x500+400+200")

def show_btn(b):
    messagebox.showinfo(message=f"{b.cget('text')}")
    b.config(command=None)

for x in range(3):
    btn = Button(root, text=f"{x}")
    btn.config(command=lambda b=btn: show_btn(b))
    btn.pack()

root.mainloop()

How about

b.config(state="disable")

to disable button.

It will be also grayed.

And later you can activate it again

b.config(state="normal")

from tkinter import *
from tkinter import messagebox

root = Tk()
root.geometry("500x500+400+200")

def show_btn(b):
    messagebox.showinfo(message=f"{b.cget('text')}")
    b.config(state="disable")
    #b["state"] = "disable"

def activate():
    for btn in all_buttons:
        btn.config(state="normal")
        #btn["state"] = "normal"

all_buttons = []

for x in range(3):
    btn = Button(root, text=f"{x}")
    btn.config(command=lambda b=btn: show_btn(b))
    btn.pack()
    all_buttons.append(btn)

Button(root, text="Activate Again", command=activate).pack()

root.mainloop()