Tkinter is not being stopped by sleep. Why?

Question

Thanks for taking the time to read this. I'm making a python project that automatically opens my meet links for class! The whole thing went well, but now i want a loading screen. Imagine this:

New window pops up Label appears: "Welcome to google meet!" i slowly config the label using time.sleep() to decrease visibility. then the label gets replaced by my app GUI! Sounded great in my head! Until i built it. The Time.sleep wasnt working, and it automatically skips to the next stage: GUI! and if i remove the gui part, it just stays blank.

My code:

#----------------SETUP-----------------------
from datetime import datetime

import pickle
from tkinter import *
import webbrowser

import datetime
import time
# all my imports
m = Tk()

W = Label(m, text="Welcome to google meet!", fg="#000000")
time.sleep(0.2)
W.pack()
time.sleep(1.2)
W.config(fg="#434343")

time.sleep(0.2)
W.config(fg="#8c8c8c")

time.sleep(0.2)
W.config(fg="#d2d2d2")

time.sleep(0.2)
W.config(fg="#eeeeee")

time.sleep(0.2)
W.config(fg="#ffffff")
W.destroy()


def Load():
    w=Button(m, text="Open meet",bg="#F0F0F0", highlightthickness = 0, bd = 0)
    m.title("Meet for Aparicio by ")
    top = Tk()
    top.title("Club Form")
    copyrightt = Label(m, text="All rights reserved. Copyright by  . Do not distribute as your own, but link to the google docs.")
    L2 = Label(top, text="If this is your first time using this app, please fill out the form. If not, you can just ignore it.")
    L2.pack()
    copyrightt.pack()
    ba = Button(top, text="Submit!") # there was a ,command=submit) but since i deleted the command, i just remvoed this for now, since i only need the GUI.
    L3 = Label(top, text="Academic club link")
    L3.pack()
    E2 = Entry(top, bd =5)
    E2.pack()



    L5 = Label(top, text="Pastoral link")
    L5.pack()
    E4 = Entry(top, bd =5)
    E4.pack()




    L7 = Label(top, text="Interest link")
    L7.pack()
    E6 = Entry(top, bd =5)
    E6.pack()
    ba.pack()
    m.geometry("700x250")
    label = Label(m,text="Press the button below to open the link!")
    img = PhotoImage(file="C:/Users/PKSNFL/Documents/Untitled.png") # make sure to add "/" not "/"

    label.pack()
    w.config(image=img)
    w.pack()
    wekday = datetime.datetime.today().weekday()

    if wekday == 3:
        l2 = Label(m, text="DISCLAIMER: IF YOU RUN THIS TWICE FROM 1:00 PM TO 2:00 PM, MESSAGE    ON HOW TO FIX IT.")
        l3 = Label(m, text="If you don't, the app will give you the wrong link for the rest of its life until you fix it :D")
        l2.pack()
        l3.pack()
Load()
#--------------------------------------------

#
m.mainloop()

I have cut out the code for my meet, and it has no relation to my tkinter code, except for the submit button.

Please post a [mcve]. This is missing imports and some definitions to reproduce the issue. — Mark Tolonen, Apr 11 '22 at 03:04
The only thing `time.sleep()` does in a Tkinter application is lock up the GUI, preventing any screen updates from happening. Tkinter provides an `.after()` method for scheduling function calls to occur in the future, which is the appropriate approach here. — jasonharper, Apr 11 '22 at 03:21
There are many very similar questions on this site, all about how sleep seems to freeze tkinter. Have you done any research before asking this question? — Bryan Oakley, Apr 11 '22 at 03:59
@BryanOakley... Yes. Not really on this site, but other public sites like tutorialspoint or geeksforgeeks — A Pickacks, May 02 '22 at 02:25

Sriram Srinivasan · Accepted Answer · 2022-04-11T06:47:02.100

As mentioned in one of the comments, time.sleep locks the GUI and prevents any screen updates from taking place. If you want to schedule GUI function calls, you must use:

<widget>.after(<delay-in-milliseconds>, <function>)

I have used a constant sleep duration of 0.2 seconds to achieve the transition. You can modify the durations according to your preference.

time = int(sum(sleep_times[:i+1]) * 1000)

calculates the cumulated time from the start of the transition.

The reason for using lambda clr = fg_clrs[i]: W.config(fg = clr) instead of lambda : W.config(fg = fg_clrs[i]) is explained in this answer.

Working Code:

from tkinter import *

root = Tk()
root.geometry("600x500")
fg_clrs = ("#000000", "#434343", "#8c8c8c", "#d2d2d2", "#eeeeee", "#ffffff")
sleep_times = (0.2,) * 6
label = Label(root, text="Welcome to google meet!", fg="#000000")
label.pack()

for i in range(len(sleep_times)):
    time = int(sum(sleep_times[:i+1]) * 1000) 
    root.after(time, lambda clr = fg_clrs[i]: label.config(fg = clr))

root.mainloop()

Tkinter is not being stopped by sleep. Why?

1 Answers1

Working Code: