python-selenium Page

#用page object思想实现百度首页的搜索和登陆功能
from selenium import webdriver
from selenium.webdriver.common.keys import Keys
import time
class BaiduPage():
    url='http://www.baidu.com/'
    username='XXXXXX'
    password='******'
    
    def __init__(self,driver):
        self.driver=driver  
              
    def search(self,kw='51cto'):
        self.driver.get(self.url)
        time.sleep(2)
        self.driver.find_element_by_id('kw').send_keys(kw)
        self.driver.find_element_by_id('su').click()
        time.sleep(2)
        
    def login(self,username=None,password=None):
        
        if username==None:
            username=self.username
        if password==None:
            password=self.password
        self.driver.get(self.url)
        time.sleep(2)
        self.driver.find_element_by_link_text('登录'.decode('utf-8')).click()
        time.sleep(2)
        self.driver.find_element_by_id('TANGRAM__PSP_8__userName').send_keys(self.username)
        self.driver.find_element_by_id('TANGRAM__PSP_8__password').send_keys(self.password)
        self.driver.find_element_by_id('TANGRAM__PSP_8__submit').click()
        time.sleep(2)
        
    def __del__(self):
        pass
        #self.driver.quit()
        
driver=webdriver.Chrome()
page=BaiduPage(driver)
page.login()
self.driver.quit()