用python3,去定位Chrome浏览器的126邮箱输入窗口，求问我这段代码哪里错了？在线等，急！

Question

from selenium import webdriver

import time

driver=webdriver.Chrome()
driver.get("http://www.126.com")

print('Before login========')

#打印当前页面title
title=driver.title
print(title)

#打印当前页面URL
now_url=driver.current_url
print(now_url)

driver.switch_to.default_content()
driver.switch_to_frame(0)

driver.find_element_by_xpath("//div[@class='u-input box']/input[@name='email']")