Loop not starting in python

Question

The following code is to make a stopwatch in python turtle, and I am having issues with starting and stopping the watch. There is a section in which I use the .onkey command to try to start the clock with the q key, and I am having trouble getting this working. Any fixes?

import time,turtle

running = False
cl = 0

def start():
    running = True
    
def stop():
    running = False

wn = turtle.Screen()
wn.setup(width=200,height=200)
wn.bgcolor('grey')
wn.tracer(0)

timePen = turtle.Turtle()
timePen.speed(0)
timePen.color('red')
style = ('Courier', 30, 'italic')
timePen.hideturtle()
timePen.penup()

wn.listen()
wn.onkey(start,'q')
wn.onkey(stop,'w')

while running == True:
    
    time.sleep(.01)
    cl += .1
    timePen.goto(0,0)
    
    timePen.write(round(cl,2), font=style, align='center')
    wn.update()
    time.sleep(.09)
    timePen.clear()
    wn.update()
    

wn.mainloop()

Answer 1

the loop wont start because running is set to False so you must set running to true to start since a loop will start and loop aslong as the condition is true, the second issue is that the running inside the stop() and start() are a copy of the variable thus the real one that was delcared will not changed unless you declare it via global running inside the def

 import time,turtle
    
    running = True
    cl = 0
    
    def start():
        global running
        running = True
        
    def stop():
        global running
        running = False
    
    wn = turtle.Screen()
    wn.setup(width=200,height=200)
    wn.bgcolor('grey')
    wn.tracer(0)
    
    timePen = turtle.Turtle()
    timePen.speed(0)
    timePen.color('red')
    style = ('Courier', 30, 'italic')
    timePen.hideturtle()
    timePen.penup()
    
    wn.listen()
    wn.onkey(start,'q')
    wn.onkey(stop,'w')
    
    while running == True:
        
        time.sleep(.01)
        cl += .1
        timePen.goto(0,0)
        
        timePen.write(round(cl,2), font=style, align='center')
        wn.update()
        time.sleep(.09)
        timePen.clear()
        wn.update()
        
    
    wn.mainloop()