LED to blink when a push button is NOT pressed and to be continually on when the button IS pressed (Python)

Question

So, i have a LED controlled by a Raspy, and also a basic GUI with just a push button, I want it to behave as follows:

• LED blinks when the push button IS NOT pressed.
• LED should stay ON continually when the push button IS pressed.

When I execute light starts blinking, but the button does not show up. When I interrupt the program, the button shows up. Why?

from tkinter import *
import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BOARD)
GPIO.setup(8, GPIO.OUT)
GPIO.output(8, False)
buttonPressed = False

master = Tk()

def callback():
    GPIO.output(8, True)
    buttonPressed = True

w = Button(master, text="Turn on light", command = callback)
w.pack()

while True:
    if buttonPressed == False:
        GPIO.output(8, True)
        time.sleep(0.5)
        GPIO.output(8, False)
        time.sleep(0.5)
    else:
        GPIO.output(8, True)

Answer 1

I can't test it on RPi but I could be something like this.

Normal command= can recognize only when you clicked button but it can't recognize when you released it - you need to bind events <ButtonPress> and <ButtonRelease> which will run functions on "mouse left button press" and "mouse left button release"

I use after() to run function with delay so I don't need sleep() and while which can block mainloop() (and it can freeze all GUI).

And I don't need also while loop because I run all inside on_press and on_release and later after() runs turn_off_led which use after() to run turn_on_led which use after() to run again turn_off_led so it works like loop.

import tkinter as tk  # PEP8: `import *` is not preferred
import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BOARD)
GPIO.setup(8, GPIO.OUT)
GPIO.output(8, False)

button_pressed = False  # PEP8: preferred `lower_case_names`

# --- functions ---

def on_press(event):
    global button_pressed

    button_pressed = True
    GPIO.output(8, True)

def on_release(event):
    global button_pressed

    button_pressed = False
    GPIO.output(8, True)

    # run after 500ms (0.5s) instead of `sleep`
    master.after(500, blink_off)

def blink_off():
    if not button_pressed:
        GPIO.output(8, False)
        # run after 500ms (0.5s) instead of `sleep`
        master.after(500, blink_on)

def blink_on():
    if not button_pressed:
        GPIO.output(8, True)
        # run after 500ms (0.5s) instead of `sleep`
        master.after(500, blink_off)

# --- main ---

master = tk.Tk()

button = tk.Button(master, text="Turn on light")
button.pack()

# here "button" means "tk.Button" and "Button" means "mouse left button"
button.bind('<ButtonPress>',   on_press)   # mouse left button pressed on tk.Button 
button.bind('<ButtonRelease>', on_release) # mouse left button released on tk.Button

# start blinking - it will use `after()` to loop
blink_on()

master.mainloop()