from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.select import Select
import time


driver = webdriver.Firefox()
test_url = "http://sahitest.com/demo/selectTest.htm"
driver.get(test_url)
driver.maximize_window()
time.sleep(10)

# 定位下拉列表的位置
list1 = driver.find_element(By.ID, "s1Id")
# 实例化下拉列表
s1 = Select(list1)
# 根据索引选中第二个列表选项
s1.select_by_index(1)
# 根据列表选项值选中第三个选项
s1.select_by_value("o2")
# 根据列表选项的文本选中第三个选项
s1.select_by_visible_text("o3")
time.sleep(3)
driver.close()