[Tkinter-discuss] Program continuing execution while tkinter window is open

[Michael Lange]

Hi,

On Thu, 22 Sep 2022 16:17:50 +0000
Massimo POZZONI via Tkinter-discuss <tkinter-discuss at python.org> wrote:

>
> I'm wondering if there is any way to have a tkinter window running,
> while the main program is continuing its execution. I tried with
> threading but with no success.
>
> So far I always got the program to wait until the tkinter window is
> closed.
>
> Is there any way to have the python main program to continue the
> execution while a tkinter window is open?

I am not sure what you actually want to achieve; when using threads you
need to make sure that the Tcl interpreter (inside which the tkinter
window is running) runs in the main program thread and that you must
*never* do any calls to tkinter from within any of the child threads. For
interaction between tkinter and the child threads you can for example use
Lock or Condition objects to safely update some variable value from the
child thread and an after() loop to query the variable value on the Tk
side.

Below a primitive example:

##########################################

from tkinter import *
from threading import Thread, Lock
from time import sleep
from signal import signal

root = Tk()
s = IntVar()
s.set(0)
Label(root, textvariable=s).pack(pady=30, padx=70)

x = 0
run = True
lock = Lock()

def quit(*args):
    global run
    # make sure the child stops before we quit
    run = False
    root.quit()
root.protocol('WM_DELETE_WINDOW', quit)
# make sure keyboard interrupt is handled properly
signal(2, quit)

def poll():
    lock.acquire()
    s.set(x)
    print('current value ->', x)
    lock.release()
    root.after(500, poll)
poll()

def incr():
    global x
    while run:
        lock.acquire()
        x += 1
        lock.release()
        sleep(1)
    print('child thread done')

t = Thread(target=incr)
t.start()

root.mainloop()

##########################################

Have a nice day,

Michael

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