How to make a non-blocking delay on Tkinter?

Question

The following code is a stopwatch on Tkinter which has GPIO involved. I tried adding time.sleep for debouncing the button, but it also delays the stopwatch execution. Makes sense. But I just started using Python and Tkinter, so I don't know how to deal with this for now. Does anyone have a suggestion?

#!/usr/bin/env python3
import tkinter as tk
from threading import Thread
import RPi.GPIO as GPIO
import time
import serial
# GPIO BOARD PIN numbers
# setup GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
ser = serial.Serial ("/dev/ttyS0", 9600)
GPIO.setup(21, GPIO.IN)
GPIO.setup(20, GPIO.IN)
GPIO.setup(16, GPIO.IN)
GPIO.setup(26, GPIO.IN)
GPIO.setup(19, GPIO.IN)
GPIO.setup(13, GPIO.IN)
# Simple status flag
# False mean the timer is not running
# True means the timer is running (counting)
running = False
def update_timeText():
 global running
 global timer
 if running == False and GPIO.input(16) == False:
 running = True
 print('Start')
 ser.write(b'3')
 time.sleep(0.3) 
 elif running == True and GPIO.input(13) == False:
 running = False
 print('Stop')
 ser.write(b'6')
 time.sleep(0.3) 
 elif timer != [0, 0, 0] and running == False and GPIO.input(13) == False:
 timer = [0, 0, 0]
 timeText.configure(text='00:00:00') 
 elif timer != [0, 0, 0] and running == False and GPIO.input(16) == False:
 running = True
 print('Start')
 ser.write(b'3')
 time.sleep(0.3) 
 elif running == True and GPIO.input(20) == False:
 print('Speed up')
 ser.write(b'2')
 time.sleep(0.3) 
 elif running == True and GPIO.input(21) == False:
 print('Speed down')
 ser.write(b'1')
 time.sleep(0.3)
 if running:
# Every time this function is called, we will increment 1 centisecond (1/100 of a second)
 timer[2] += 1
 # Every 100 centisecond is equal to 1 second
 if (timer[2] >= 100):
 timer[2] = 0
 timer[1] += 1
 # Every 60 seconds is equal to 1 min
 if (timer[1] >= 60):
 timer[0] += 1
 timer[1] = 0
# We create our time string here
 timeString = pattern.format(timer[0], timer[1], timer[2])
# Update the timeText Label box with the current time
 timeText.configure(text=timeString)
# Call the update_timeText() function after 1 centisecond
 root.after(10, update_timeText)
# To start the timer
def start():
 global running
 running = True
# To pause the kitchen timer
def pause():
 global running
 running = False
# To reset the timer to 00:00:00
def reset():
 global timer
 timer = [0, 0, 0]
 timeText.configure(text='00:00:00')
# To exit our program
def exit():
 root.destroy()
def exitt(event):
 root.destroy()
root = tk.Tk()
root.attributes("-fullscreen",True)
root.wm_attributes("-topmost",1)
root.bind("<Escape>", exitt)
button_frame = tk.Frame(root)
button_frame.pack(fill=tk.X, side=tk.BOTTOM)
start_button = tk.Button(button_frame, text='Start', command=start, width = 12 , height = 3,bg="green")
stop_button = tk.Button(button_frame, text='Stop', command=pause, width = 12 , height = 3,bg="red")
reset_button = tk.Button(button_frame, text='Reset', command=reset, width = 12 , height = 3,bg="yellow")
quit_button = tk.Button(button_frame, text='Quit', command=exit, width = 12 , height = 3,bg="grey")
button_frame.columnconfigure(0, weight=1)
button_frame.columnconfigure(1, weight=1)
button_frame.columnconfigure(2, weight=1)
button_frame.columnconfigure(3, weight=1)
start_button.grid(row=0, column=0, sticky=tk.W+tk.E)
stop_button.grid(row=0, column=1, sticky=tk.W+tk.E)
reset_button.grid(row=0, column=2, sticky=tk.W+tk.E)
quit_button.grid(row=0, column=3, sticky=tk.W+tk.E)
# Our time structure [min, sec, centsec]
timer = [0, 0, 0]
# The format is padding all the 
pattern = '{0:02d}:{1:02d}:{2:02d}'
# Create a timeText Label (a text box)
timeText = tk.Label(root, text="00:00:00", font=("Helvetica", 150))
timeText.pack()
update_timeText()
root.mainloop()

• Matt: You'll need to use multithreading to do that. I'll write an answer for ya when I'm off mobile

Answer 1

To 'debounce' a button in tkinter your main script must be continuing to run the root.mainloop loop (as opposed to being stuck in a function call).

To do that you can call button functions in a new thread, allowing the main thread to continue running the main loop.

Here is an example of calling a function in a new thread:

import tkinter as tk
from threading import Thread
from time import sleep
def print_hello():
 print("Hello")
 sleep(3)
 print("Done")
root = tk.Tk()
container = tk.Frame(root)
container.pack(fill="both", expand=True)
container.grid_rowconfigure(0, weight=1)
container.grid_columnconfigure(0, weight=1)
frame_main = tk.Frame(container)
frame_main.grid(row=0, column=0, sticky="NSEW")
button_hello = tk.Button(frame_main, text="Say Hello", command=lambda: Thread(target=print_hello).start())
button_hello.grid(sticky="NSEW")
root.mainloop()

Notice how you can call the function multiple times before it finishes running.