Image in label does not immideately change after function call

Question

Im currently trying to change an image in a tkinter label widget by using a binding to the return key. After pressing the return key I would like the image to change to "im2", then wait for 2 seconds and change again to "im3". The code I use so far is:

window = tk.Tk()
window.title("Testwindow")
window.geometry("800x800")
window.configure(background='grey')

# images
im1_path = "im1.gif"
im2_path = "im2.gif"
im3_path = "im3.gif"
im1 = ImageTk.PhotoImage(Image.open(im1_path))
im2 = ImageTk.PhotoImage(Image.open(im2_path))
im3 = ImageTk.PhotoImage(Image.open(im3_path))

panel = tk.Label(window, image = im1)
panel.pack(side = "bottom", fill = "both", expand = "yes")

def callback(e):
    panel.configure(image = im2)
    panel.image = im2

    time.sleep(2)

    panel.configure(image = im3)
    panel.image = im3

window.bind("<Return>", callback)
window.mainloop()

But instead of changing the image twice it is only changed once to "im3" 2 seconds after pressing return, so somehow the first change is not displayed. Does anyone know why?

Changes are not reflected in the UI so long as it is executing your code. Updates only happen in `mainloop()`. — msw, Jun 12 '16 at 13:36
Also see http://stackoverflow.com/questions/30284270/why-does-time-sleep-pause-tkinter-window-before-it-opens and http://stackoverflow.com/questions/33175457/time-sleep-equivalent-on-tkinter — PM 2Ring, Jun 12 '16 at 13:36
You may also find this example helpful: http://stackoverflow.com/a/32766256/4014959 — PM 2Ring, Jun 12 '16 at 13:47

hashcode55 · Accepted Answer · 2016-06-12T13:33:16.080

time.sleep() won't work here as it stops the execution of the program, you'll have to use after...and its also a bad practice to use sleep in GUI programming.

root.after(time_delay, function_to_run, args_of_fun_to_run)

So in your case it'll like

def change_image():
    panel.configure(image = im3)
    panel.image = im3

and in your callback function

def callback(e):
    panel.configure(image = im2)
    panel.image = im2
    #after 2 seconds it'll call the above function
    window.after(2000, change_image)

Image in label does not immideately change after function call

1 Answers1