python 打开页面页面的链接，为什么总是报错呀？

打开页面页面的链接，为什么总是报错呀？代码如下

driver = webdriver.Firefox()driver.get("http://www.baidu.com") # 加载页面links = driver.find_element_by_xpath("//a")print (links)length = len(driver.find_elements_by_tag_name("a"))print (length)for i in range(0, length): links = driver.find_elements_by_tag_name("a") link = links[i] print("1",link) if not ("_blank" in link.get_attribute("target") or "http" in link.get_attribute("href") or "javascript" in link.get_attribute("href")): link.click() sleep(2) print(link) driver.back() else: print("1")