Why can't I use time.sleep with tkinter

Question

I wanted the label to display red color then blue after a second but that's not happening
from tkinter import*
import time
w=Tk()
l=Label(w)
l.pack()
while True:
l.config(bg='red')
time.sleep(1)
l.config(bg='blue')
w.mainloop()

Answer 1

from time import time, sleep
from Tkinter import *

refer to stackoverflow
https://stackoverflow.com/a/10393929/7218253

Answer 2

Most tkinter widgets have a method widgetname.after().This takes in the time in microseconds and a callback function
For example,
from tkinter import *
root = Tk()
label = Label(root,bg='red')
label.pack()
def change_color():
label.config(bg='blue')
label.after(200,change_color)
root.mainloop()

Answer 3

//Where did you tried sololearn code playground or in external IDE