import cv2
import numpy as np

def draw_circle(event, x, y, flags, param):
    print type(param[0]), param[1]
    if event == cv2.EVENT_MOUSEMOVE:
        cv2.circle(param[0], (x,y), 100, (255,255,255), -1)

img = np.zeros((512,512,3), np.uint8)
a = []
cv2.namedWindow('image')
cv2.setMouseCallback('image', draw_circle, [img, a])

while(1):
    cv2.imshow('image',img)
    if cv2.waitKey(20) & 0xFF == 27:
        break
cv2.destroyAllWindows()