Create the following script, painting.py:

#!/usr/bin/python3 
#painting.py 
import tkinter as TK 
 
#Set defaults 
btn1pressed = False 
newline = True 
 
def main(): 
  root = TK.Tk() 
  the_canvas = TK.Canvas(root) 
  the_canvas.pack() 
  the_canvas.bind("<Motion>", mousemove) 
  the_canvas.bind("<ButtonPress-1>", mouse1press) 
  the_canvas.bind("<ButtonRelease-1>", mouse1release) 
  root.mainloop() 
 
def mouse1press(event): 
  global btn1pressed 
  btn1pressed = True 
 
def mouse1release(event): 
  global btn1pressed, newline 
  btn1pressed = False 
  newline = True 
 
def mousemove(event): 
  if btn1pressed == True: 
    global xorig, yorig, newline 
    if newline == False: 
      event.widget.create_line(xorig,yorig,event.x,event.y, 
                               smooth=TK.TRUE) 
    newline = False 
    xorig = event.x 
    yorig = event.y 
 
if __name__ == "__main__": 
  main() 
#End