切换到新窗口不工作selenium，python

Question

import unittest
from selenium import webdriver
from selenium.webdriver.common.keys import Keys
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
import time


class slTest(unittest.TestCase):

def test_santi(self):
      self.browser=webdriver.Ie("C:\Users\chethan\Documents\IEDriverServer.exe")
    self.browser.implicitly_wait(5)
    self.browser.get("http://myqesite.com/banners.php")

    #vr=self.browser.execute_script("return initValues")
    curr=self.browser.current_window_handle
    print curr
    num=0
    res=self.browser.find_element_by_id("productcontainer")
    links=res.find_elements_by_tag_name("a")
    for link in links:
        link.click()
        time.sleep(2)
        open_windows = self.browser.window_handles
        self.browser.switch_to_window(open_windows[-1])
        print "current: ", self.browser.current_url


        print link.get_attribute("id")
        #print self.browser.current_url
        num=num+1

    print num
    #self.browser.quit()


if __name__ == "__main__":
unittest.main()

点击每个链接后，将打开一个新窗口，需要通过使用switch_to_window来打开每个窗口的URL。

请有人帮我解决这个问题

提前致谢