tkinter Label不显示

def work():
    tk = Tk()
    tk.update()
    print(tk.winfo_screenwidth(),tk.winfo_screenheight())
    tk.geometry('{}x{}'.format(tk.winfo_screenwidth(),tk.winfo_screenheight()))
    tk.attributes("-topmost", True)
    tk.attributes("-fullscreen",True)
    tk.mainloop()
    timeLabel = Label(tk,text = str(0) + ':' + str(5))
    timeLabel.pack(fill = BOTH,expand = True)
    for i in range(5):
        time.sleep(1)
        timeLabel.config(text = str(0) + ':' + str(5 - i))
    tk.destroy()

运行的时候timeLable并没有显示出来
请问如何显示timeLable？并且还要显示在中间

mainloop后面的都执行不到，上面都是无限循环了，后面的你不关了窗口根本不执行

from tkinter import *

def countdown(n):
    n = n -1
    timeLabel["text"] = str(n).zfill(2)
    if n == 0:
        timeLabel["text"] = "火箭发射"
        return None
    timeLabel.after(1000,countdown,n)
    
        


tk = Tk()

timeLabel = Label(tk,text = "05")
timeLabel.pack(expand =1,fill="both")
timeLabel.after(1000,countdown,5)

tk.mainloop()