Python Tkinter canvas update

Question

I want to update the color of a circle in Tkinter in python 2. I can make my circle but the color does not update in my task() method until I stop running the program. How can I make the color update as soon as val is greater than 4?

from Tkinter import *
m = Tk()
w = Canvas(m, width = 100, height = 100)
w.pack()
cir = w.create_oval(50, 50, 100, 100)

def task():
    while True:
        val += 1
        if val > 4:
            w.itemconfig(cir, fill = "blue")

m.after(2000, task)
m.mainloop()

You have a while True: with no break. What did you expect? — TigerhawkT3
– TigerhawkT3, Commented Jul 20, 2015 at 21:36
I wrote the code wrong the first time but even with this fix it still doesnt update color — Brosten
– Brosten, Commented Jul 20, 2015 at 21:50
You still have a while True: with no break. Again, what did you expect? — TigerhawkT3
– TigerhawkT3, Commented Jul 20, 2015 at 21:55
@Brosten Please don't ninja-edit your question -- by adding indentation after people were already helping, you changed the code and rendered existing feedback redundant at best, and confusing at worst. — DreadPirateShawn
– DreadPirateShawn, Commented Jul 20, 2015 at 22:02
Given the code change, I'm removing my answer. Note that the problem lies in what @TigerhawkT3 identified in comments on that answer -- namely, you're hogging an entire CPU core to increment val as fast as it can, basically freezing your program unless you go into multiprocessing/threading. What you're trying to ask is how to refresh the display between each while True cycle. — DreadPirateShawn
– DreadPirateShawn, Commented Jul 20, 2015 at 22:07

devramon22 · Accepted Answer · 2015-07-20 22:41:08Z

1

This will work.

Like @TigerhawkT3 said you need a break to exit the loop.

from Tkinter import *
m = Tk()
w = Canvas(m, width = 100, height = 100)
w.pack()
cir = w.create_oval(50, 50, 100, 100)

def task():
    val = 1
    while True:
        val += 1
        if val > 4:
            w.itemconfig(cir, fill = "blue")

            #without the break task will run forever
            break

m.after(2000, task)
m.mainloop()

answered Jul 20, 2015 at 22:41

devramon22

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TigerhawkT3 Over a year ago

The OP commented in a now-deleted answer that he wants to keep incrementing val even after changing the fill color (didn't explain why, though).

Guydangerous99 · Accepted Answer · 2017-11-29 15:13:31Z

0

I'm afraid you'll have to do it the long way, and the only way. Code:

from tkinter import *

m = Tk()

c = Canvas(root, width=100, height=100)
c.pack()

v = 4

if v == 4:
    v = 0
    c.pack_forget()
    del c

    c = Canvas(root, width=100, height=100, bg='blue')
    c.pack()

c.mainloop()

Do all the changing with v (I haven't put that in though)! Hope this helps!

answered Nov 29, 2017 at 15:13

Guydangerous99

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1 Comment

Guydangerous99 Over a year ago

Wait, I didn't mean v, I meant val, sorry!

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