python+selenium自动化软件测试：Message: Element could not be scrolled into view

# coding:utf-8
from selenium import webdriver
from selenium.webdriver.common.action_chains import ActionChains
from selenium.webdriver.support.select import Select
driver = webdriver.Firefox()
url = "https://www.baidu.com"
driver.get(url)
driver.implicitly_wait(20)
# 鼠标移动到“设置”按钮
mouse = driver.find_element_by_link_text("设置")
ActionChains(driver).move_to_element(mouse).perform()
driver.find_element_by_link_text("搜索设置").click()
s = driver.find_element_by_id("nr")
Select(s).select_by_visible_text("每页显示50条")

会出现Message: Element could not be scrolled into view。

让脚本sleep一下，等页面加载完就可以了：

# coding:utf-8
from selenium import webdriver
from selenium.webdriver.common.action_chains import ActionChains
from selenium.webdriver.support.select import Select
import time    
driver = webdriver.Firefox()
url = "https://www.baidu.com"
driver.get(url)
driver.implicitly_wait(20)
# 鼠标移动到“设置”按钮
mouse = driver.find_element_by_link_text("设置")
ActionChains(driver).move_to_element(mouse).perform()
driver.find_element_by_link_text("搜索设置").click()
s = driver.find_element_by_id("nr")
time.sleep(10)
Select(s).select_by_visible_text("每页显示50条")