How to check for a button press while another tk.button function runs?

Question

I am currently creating a GUI with tkinter for a tilt table in my lab. I have up and down buttons programmed to turn a pin on until the table reaches a certain angle, which is read in from an inclinometer via Arduino, and then turn the pin off. So currently the function associated with each button repeatedly reads in the angle until the correct angle is reached, but I also want to be able to turn off the pin whenever I choose. The problem is that while the function associated with Up is running, the program is not checking for any button presses. How can I get the pause button to interrupt the function?

I've tried to implement interrupts with the threading library, but it seems tkinter won't let any other code run while the function associated with a button() is running.

import tkinter as tk from tkinter import * import RPi.GPIO as GPIO import time import serial global read_serial win = Tk() def Up(): if read_serial < target: global read_serial #read_serial is edited elsewhere not included here GPIO.output(40,GPIO.HIGH) time.sleep(.05) read_serial=ser.readline().rstrtip().decode("utf-8") read_serial=float(read_serial) Up() else: GPIO.otuput(40,GPIO.LOW) def Pause(): GPIO.output(40,GPIO.LOW) upButton = Button(win,text='UP',command=Up) pauseButton = Button(win,text='PAUSE',command=Pause) upButton.grid(row=1) pauseButton.grid(row=2) win.mainloop()

I didn't want to paste too much code but if I'm missing any crucial parts I can include more. I want to interrupt Up() when I press Pause, but once I press Up, the program ignores any input until read_serial is greater than target. Is it possible to implement an interrupt to check for other button presses with tkinter?

@BlackThunder Thread(target=?) would my target be Pause or pauseButton? — BenS
– BenS, Commented Aug 28, 2019 at 14:54
I don't use threadings so you have to figure it out yourself — Nouman
– Nouman, Commented Aug 28, 2019 at 14:55
Threading isn't the only answer, but you must actually return from your button commands fairly quickly if the GUI is to remain responsive. Any ongoing activity could be performed in a thread, or done a little piece at a time in a function that you schedule later via .after() (and it can reschedule itself with .after() if the activity still isn't finished). — jasonharper
– jasonharper, Commented Aug 28, 2019 at 14:56
You could probably just use win.after(0, Up) instead of calling Up() directly. — tobias_k
– tobias_k, Commented Aug 28, 2019 at 15:42

enchant97 · Accepted Answer · 2019-08-28 18:16:22Z

The easiest to run a function in the background when using tkinter is to use the .after() method, this allows for you not to need the threading module. The 0 in the .after() is the number of ms to wait until it executes the function given.

example (not the best way as it now has another function):

def bnt_up(): win.after(0, Up) upButton = Button(win,text='UP',command=bnt_up)

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