Exemplo tkinter utilizando o método after (Callback)

main.py

from tkinter import *
from time import sleep
cont=0

def clicou():
    global cont
    while True:
        cont+=1
        conta_label.config(text=f"contando: {cont}")
        print(cont)
        sleep(1)
        if cont <= 10:
            break

janela = Tk()
janela.geometry("200x100")
conta_label = Label(janela, text="contando: 0")
conta_label.grid(row=8, column=0, padx=8, pady=15)
fn_clicou = lambda : janela.after(100, lambda: clicou())
botao = Button(janela, text="Iniciar", command=fn_clicou)
botao.grid(column=0, row=10, padx=15, pady=15)
janela.mainloop()