Implementing button release for a stopwatch with Tkinter

I have designed a program that allows three buttons to control a stopwatch:

• Start button, starts the timer: Canvas turns green (in progress), if timer reaches 15 seconds canvas will turn red.
• Stop button, resets the timer: Canvas turns yellow (idle).
• Emergency Stop button: When pressed, pauses timer (canvas turns orange). When released, resumes timer (canvas turns green).

Currently the Start & Stop buttons work fine. But the Emergency Stop (pause & resume) is where I am having issues.

If I start the timer say for 5 seconds and then press the Emergency Stop button to pause the timer, the timer does pause, but releasing the button causes the program to loop in the section that prints "Release" and doesn't restart the timer.

I am expecting the release of the Emergency Stop button to resume the timer turning the canvas green if below 15 seconds.

I am having struggle debugging the program as once in a tkinter loop you can't really see what buttons are being selected and where you are going with the program.

Here is the code I have written for this:

class StopWatch(tk.Frame):
def __init__(self, parent=None, **kw):
tk.Frame.__init__(self, parent, kw)
self._start = 0.0
self._elapsedtime = 0.0
self._running = 0
self._timer_text = tk.StringVar()
self._timer_text.set("00:00:00")
self._canvas_color = tk.StringVar()
self._canvas_color.set("yellow")
self.grid(sticky=tk.NSEW)
self.timer_label = tk.Label(self, textvariable=self._timer_text, font=("Helvetica", 48))
self.timer_label.grid(row=0, column=1, pady=10, padx=10)
self.canvas = tk.Canvas(self, width=100, height=100, bg="yellow", highlightthickness=0)
self.canvas.grid(row=0, column=0, pady=10, padx=10
GPIO.add_event_detect(14, GPIO.FALLING, callback=self.start, bouncetime=50)
GPIO.add_event_detect(15, GPIO.FALLING, callback=self.reset, bouncetime=50)
GPIO.add_event_detect(21, GPIO.FALLING, callback=self.pause, bouncetime=200)
def _update(self):
"""Update the timer label with elapsed time."""
self._elapsedtime = time.time() - self._start
self._timer_text.set(time.strftime('%H:%M:%S', time.gmtime(self._elapsedtime)))
if self._elapsedtime > 15:
self.canvas.config(bg='red')
if self._running:
self.after(100, self._update)
def start(self, channel):
"""Start the stopwatch."""
self._start = time.time() - self._elapsedtime
self._running = 1
self.canvas.config(bg='green')
self._update()
def pause(self, channel):
"""Pause the stopwatch."""
self._running = 0
self.canvas.config(bg='orange')
eStop_flag = True
while eStop_flag == True:
print("Stop flag True")
time.sleep(0.2)
if GPIO.input(21) != GPIO.LOW:
print("Emergency Stop")
time.sleep(0.5)
eStop_resume = False
while eStop_resume == False:
if GPIO.input(21) != GPIO.HIGH:
print("Released")
eStop_resume == True
time.sleep(1)
eStop_flag == False
self.start(channel)
def reset(self, channel):
"""Reset the stopwatch."""
self._start = time.time()
self._elapsedtime = 0.0
self._timer_text.set("00:00:00")
self._running = 0
self.canvas.config(bg='yellow')
if __name__ == '__main__':
root = tk.Tk()
root.title('Stopwatch')
root.geometry('500x200')
stopwatch = StopWatch(root)
stopwatch.pack(expand=True, fill=tk.BOTH)
root.mainloop()

In the pause function you are using double equals instead of a single one. It should look like this:

def pause(self, channel):
"""Pause the stopwatch."""
self._running = 0
self.canvas.config(bg='orange')
e_stop_flag = True                # Variables should be lowercase
while e_stop_flag:                # This is a Boolean variable, so you don't  
# need a conditional statement
print("Stop flag True")
time.sleep(0.2)
if GPIO.input(21) != GPIO.LOW:
print("Emergency Stop")
time.sleep(0.5)
e_stop_resume = False
while not e_stop_resume:    # Same here (but use "not")
if GPIO.input(21) != GPIO.HIGH:
print("Released")
e_stop_resume = True  # this should set the var so use = 
time.sleep(1)
e_stop_flag = False               # Same here
self.start(channel)

(I don't know what GPIO is)