硒代码不会终止

Question

以下代码不会终止。可能是什么原因呢？from selenium import webdriverfrom selenium.webdriver.common.keys import Keysdriver = webdriver.Firefox()driver.get("http://www.quora.com/physics")elem = driver.find_element_by_class_name("cancel")#ele=elem[0]print "done"