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

flypadre

I've been working on some python scripts accessing the gpio pins on my rpi to light an led and I ran into a little problem I'm not sure how to solve.

My code looks something like this minus some setup statements

 

def ledblink():

     while True:

          GPIO.output(13, True)

          time.sleep(.5)

          GPIO.output(13, False)

          time.sleep(.5)

 

def ledoff():

     GPIO.output(13, False)

 

button = Button(root, text = 'LED ON', command = ledblink)

button.pack()

offbutton = Button(root, text = 'LED OFF', command = ledoff)

offbutton.pack()

 

As you can probably tell using tkinter for my gui. Also, as you can probably tell once I click the on button, that is all this program is going to let me do, the led blinks and continues because True is always True. How can I keep an indefinite loop running so that I can have a blinking led and still be able to break out of the loop when I want to turn things off? This was easy when I wanted to simply turn the led on and off, but not so easy with the loop I have to make it blink.

Just an FYI I was able to break out of the loop in my script version by using a try/except in which I used KeyboardInterrupt to call GPIO.cleanup() but I'm not sure how to do this in a gui.

 

 

 

Parents
  • 0

    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()

  • Former Member
    0 Former Member in reply to flypadre

    There are a few redundant parts used here, try:

     

        import tkinter as tk 

        import time 

         

        root = tk.Tk() 

        switch = False 

         

        def blink(): 

            while switch == True: 

                print('BLINK...BLINK...') 

                time.sleep(0.5)   

         

        def switchon(): 

            switch = True 

            blink() 

         

        def switchoff(): 

            switch = False 

            blink() 

         

        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()

     

    ------------------------------------------------------------------------------------------------------

    Theres no need to add the switch into the function definition arguments, because its already being declared outside the functions its already globally used in the script and is causing confusion when declaring blink() function.

     

    When I get chance later this afternoon I'll recreate a working example again and post the entire script rather than just a snippet so you can see it working. Where about are you looking for the "blink.....blink" text to be printed? It should come out in the console you used to launch your script (if you launch it without using a console/terminal you probably wont ever see the text)

Reply
  • Former Member
    0 Former Member in reply to flypadre

    There are a few redundant parts used here, try:

     

        import tkinter as tk 

        import time 

         

        root = tk.Tk() 

        switch = False 

         

        def blink(): 

            while switch == True: 

                print('BLINK...BLINK...') 

                time.sleep(0.5)   

         

        def switchon(): 

            switch = True 

            blink() 

         

        def switchoff(): 

            switch = False 

            blink() 

         

        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()

     

    ------------------------------------------------------------------------------------------------------

    Theres no need to add the switch into the function definition arguments, because its already being declared outside the functions its already globally used in the script and is causing confusion when declaring blink() function.

     

    When I get chance later this afternoon I'll recreate a working example again and post the entire script rather than just a snippet so you can see it working. Where about are you looking for the "blink.....blink" text to be printed? It should come out in the console you used to launch your script (if you launch it without using a console/terminal you probably wont ever see the text)

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