How to break out of a while True: loop with a button

OK This is what I thought I was being asked to do with regards to coding this without using threads, but this does not work either.

import tkinter as tk
import time

root = tk.Tk()
switch = False

def blink(switch):
    while switch == True:
        print('BLINK...BLINK...')
        time.sleep(0.5)
    while switch == False:
        break

def switchon():
    switch = True
    blink(switch)

def switchoff():
    switch = False
    blink(switch)

def kill():
    root.destroy()

onbutton = tk.Button(root, text = "Blink ON", command = switchon)
onbutton.pack()
offbutton =  tk.Button(root, text = "Blink OFF", command = switchoff)
offbutton.pack()
killbutton = tk.Button(root, text = "EXIT", command = kill)
killbutton.pack()

root.mainloop()

Here's an entire working code that you can save and run, I have used a thread for ease of use and responsiveness as well as system efficiency. There are really only 4 extra lines of code to produce the threaded alternative, I also added a few extra bits here and there. Making global variables writeable within functions for simplicity. Any questions please just ask! I'm here to help rather than say what you should/shouldn't be doing, I'll always respond by providing tested functioning code

import Tkinter as tk  
import time
import threading

switch = True
root = tk.Tk()

def blink():
 def run():
  while (switch == True):
   print('BLINK...BLINK...')
   time.sleep(0.5)
   if switch == False:
    break
 thread = threading.Thread(target=run)
 thread.start()

def switchon():  
 global switch
 switch = True
 print 'switch on' 
 blink()  
      
def switchoff():  
 print 'switch off'
 global switch
 switch = False    
      
def kill():  
 root.destroy()  
      
onbutton = tk.Button(root, text = "Blink ON", command = switchon)  
onbutton.pack()  
offbutton =  tk.Button(root, text = "Blink OFF", command = switchoff)  
offbutton.pack()  
killbutton = tk.Button(root, text = "EXIT", command = kill)  
killbutton.pack()  
      
root.mainloop()

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RE: How to break out of a while True: loop with a button

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Here's an entire working code that you can save and run, I have used a thread for ease of use and responsiveness as well as system efficiency. There are really only 4 extra lines of code to produce the threaded alternative, I also added a few extra bits here and there. Making global variables writeable within functions for simplicity. Any questions please just ask! I'm here to help rather than say what you should/shouldn't be doing, I'll always respond by providing tested functioning code

import Tkinter as tk  
import time
import threading

switch = True
root = tk.Tk()

def blink():
 def run():
  while (switch == True):
   print('BLINK...BLINK...')
   time.sleep(0.5)
   if switch == False:
    break
 thread = threading.Thread(target=run)
 thread.start()

def switchon():  
 global switch
 switch = True
 print 'switch on' 
 blink()  
      
def switchoff():  
 print 'switch off'
 global switch
 switch = False    
      
def kill():  
 root.destroy()  
      
onbutton = tk.Button(root, text = "Blink ON", command = switchon)  
onbutton.pack()  
offbutton =  tk.Button(root, text = "Blink OFF", command = switchoff)  
offbutton.pack()  
killbutton = tk.Button(root, text = "EXIT", command = kill)  
killbutton.pack()  
      
root.mainloop()

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RE: How to break out of a while True: loop with a button

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Great! That should work.

One little suggestion: Move the "blink ()" call to the main at the bottom. Then you start the blink thread only once. As I read it (with my limited python knowledge), you will now start a new thread each time the "start blinking" button is pressed. So after turning it on and off again 5 times, there will be five threads  doing the blinking. This gives 5 times the output in the current incantation and a messy 5 blinking attempts through each other once you blink a real led....

Furthermore, it would be neater to stop the thread in the kill function.

Hey, another Toaru Majutsu fan?

Yes

ps. Its good to see somebody else's perspective followed up with a working example, shows how a persons coding is unique and individual to them as their fingerprints are!!

That was great, I was looking at different threading examples online but never found anything as simple as what you just presented. Really appreciate the example!