Mouse click events on a live stream with Opencv and python

This is a code that I'm using to draw a rectange in videos.

The code works like that:

1. click on video and the script save the start point
2. click again and the script save the end point and draw the rectangle

3. click again to start drawing another retangle

   import numpy as np
   import cv2
   
   rect = (0,0,0,0)
   startPoint = False
   endPoint = False
   
   def on_mouse(event,x,y,flags,params):
   
       global rect,startPoint,endPoint
   
       # get mouse click
       if event == cv2.EVENT_LBUTTONDOWN:
   
           if startPoint == True and endPoint == True:
               startPoint = False
               endPoint = False
               rect = (0, 0, 0, 0)
   
           if startPoint == False:
               rect = (x, y, 0, 0)
               startPoint = True
           elif endPoint == False:
               rect = (rect[0], rect[1], x, y)
               endPoint = True
   
   cap = cv2.VideoCapture('../videos/sample.avi')
   waitTime = 50
   
   #Reading the first frame
   (grabbed, frame) = cap.read()
   
   while(cap.isOpened()):
   
       (grabbed, frame) = cap.read()
   
       cv2.namedWindow('frame')
       cv2.setMouseCallback('frame', on_mouse)    
   
       #drawing rectangle
       if startPoint == True and endPoint == True:
           cv2.rectangle(frame, (rect[0], rect[1]), (rect[2], rect[3]), (255, 0, 255), 2)
   
       cv2.imshow('frame',frame)
   
       key = cv2.waitKey(waitTime) 
   
       if key == 27:
           break
   
   cap.release()
   cv2.destroyAllWindows()