How stop sketch in tkinter canvas - python-3.x

Question

I have few line of code here which draw circle in tkinter canvas but want i want to do is to stop the sketch to the point where it started so i use sleep but i stop the sketch where it has gotten to then it continue.
So i wrote this function
def stop_extent():
canvas.create_arc(0, 0, 0, 0, extent=0, outline="red", tags=("arc",))
extent = float(canvas.itemcget("arc", "extent"))
extent = extent + 5.0
canvas.itemconfigure("arc", extent=extent)
canvas.after(100, stop_extent)
and set all the values to 0 but still it doesn't stopped it and the label doesn't configure too.
import tkinter as tk
import time
def change_extent():
l.config(text="sketch in progress...")
canvas.create_arc(350, 100, 220, 220, extent=0, outline="yellow", tags=("arc",))
extent = float(canvas.itemcget("arc", "extent"))
extent = extent + 5.0
canvas.itemconfigure("arc", extent=extent)
canvas.after(100, change_extent)
def stop_extent():
l.config(text="sketch stopped...")
time.sleep(10)
l.config(text="sketch stopped...")
root = tk.Tk()
root.geometry("600x400")
canvas = tk.Canvas(root, width=200, height=200, background="dodger blue")
canvas.pack(fill="both", expand=True)
l = tk.Label(canvas, bg="dodger blue", fg="white")
l.place(x=250, y=20)
b= tk.Button(canvas, text="Start sketch", command=change_extent, width=25, fg='dodger blue')
b.place(x=220, y=330)
b= tk.Button(canvas, text="stop sketch", command=stop_extent, width=25, fg='dodger blue')
b.place(x=220, y=370)
root.mainloop()

Answer 1

You can keep track of the call back generated by canvas.after in the change_extent method, and cancel it with canvas.after_cancel in the stop_extent method; in the following example, I use a global variable stop to demonstrate it.
Using time.sleep in a GUI application is generally a bad idea.
You also do not need to recreate the arc each time you want to modify its extent, but that is outside the scope of your question.
import tkinter as tk
import time
def change_extent():
global stop
l.config(text="sketch in progress...")
extent = float(canvas.itemcget(arc_item, "extent"))
canvas.itemconfigure("arc", extent=extent+5)
stop = canvas.after(100, change_extent)
def stop_extent():
l.config(text="sketch stopped...")
print(stop)
canvas.after_cancel(stop)
canvas.itemconfigure("arc", extent=0) # <- reset to straight line start
stop = None
root = tk.Tk()
root.geometry("600x400")
canvas = tk.Canvas(root, width=200, height=200, background="dodger blue")
canvas.pack(fill="both", expand=True)
arc_item = canvas.create_arc(350, 100, 220, 220, extent=0, outline="yellow", tags=("arc",))
l = tk.Label(canvas, bg="dodger blue", fg="white")
l.place(x=250, y=20)
b= tk.Button(canvas, text="Start sketch", command=change_extent, width=25, fg='dodger blue')
b.place(x=220, y=330)
b= tk.Button(canvas, text="stop sketch", command=stop_extent, width=25, fg='dodger blue')
b.place(x=220, y=370)
root.mainloop()