import cv2
import numpy as np

def draw_circle(event,x,y,flags,param):
    
    if event == cv2.EVENT_LBUTTONDOWN:
        cv2.circle(img,(x,y),100,(0,255,0),-1)
    
    if event == cv2.EVENT_RBUTTONDOWN:
    
        cv2.circle(img,(x,y),100,(0,0,255),-1)
        
    if event == cv2.EVENT_MBUTTONDOWN:
        cv2.circle(img,(x,y),100,(255,255,255),-1) 
        
cv2.namedWindow(winname='drawing')

cv2.setMouseCallback('drawing',draw_circle)

img = np.zeros((512,512,3), np.int8)

while True: 
    cv2.imshow('drawing',img)
    
    if cv2.waitKey(20) & 0xFF == 27:
        break
        
cv2.destroyAllWindows()