[Tkinter] Problem reading entry box in thread

[LeeMadeux]

Good Morning,

I am new to Python. I am trying to build a program that reads a temperature from an Entry widget once every second and performs an action based upon what that temperature is. I set up a thread to do this - but it does not like the statement where I read the value of that entry widget. If I run it outside of a thread, it works, but I do not get my GUI interface to show up (hence the use of a thread). Code is below:

#!/usr/bin/env python
from tkinter import *
from tkinter import ttk
import threading
import time

def theThread():
	global lvgTemp
	global stgUp
	global stgDn
	global stgOff
	while (True):
		s= float(lvgTemp.get())
		if ( s > 52.0 ):
			stgUp = True
		else:
			if ( s < 45.0 ):
				stgDn = True
		
		if ( s < 35.0 ):
			stgOff = True
		
		print('Stage Up: ', stgUp, ' Stage Down: ', stgDn, ' Comp Off: ', stgOff)
		time.sleep(1)

stgUp = False
stgDn = False
stgOff= False
root = Tk()
root.geometry('640x480+200+200')


lvgTmp1=ttk.Label(root, text="52.0 F")
lvgTmp1.place(x=50, y=100)
lvgTmp2=ttk.Label(root, text="45.0 F")
lvgTmp2.place(x=100, y=100)
lvgTmp3=ttk.Label(root, text="35.0 F")
lvgTmp3.place(x=150, y=100)

v = StringVar(root, value='50.0')
lvgTemp = ttk.Entry(root, textvariable=v)
lvgTemp.place(x=50, y=150)

t=threading.Thread(target=theThread)
t.start()

Thanks,
Lee

[Gribouillis]

It is not a good idea to start with tkinter by using threads. Instead of a thread, you can use itkinter's after() method to call a function after a certain delay, for example root.after(1000, myfunc) will call myfunc after 1000 milliseconds. Instead of a while True loop, use repeated calls to after().

Last, but not least, if you want to see the GUI, you need to start the root.mainloop().

[LeeMadeux]

Thanks so much for your help - yes, I found that I was missing the root.mainloop().

Also, I will look into using .after

Again - Thanks!!!

Lee...