Capture online webcam

I need someone to display earthcam.com using OPENCV in PYTHON.
Please complete the follow code.
cap = cv2.VideoCapture(url) #any earthcam.com
while (True):
ret,frame = cap.read()
cv2.imshow('frame',frame)
if cv2.waitKey(20) & 0xFF == ord('q'):
break
cap.release()
cv2.destroyAllWindows()