问使用selenium、python和whatsapp-web等待元素显示而不显示。

EN

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
import datetime

driver = webdriver.Chrome('C:/webdrivers/chromedriver.exe')
driver.get('https://web.whatsapp.com/')

# do nothing until QR code scanned and whatsapp-web is accessed
input('Enter anything after scanning QR code')

# Input the name of the user to track
name = input('Enter the name of the user : ')

# find the whatsapp user to be tracked then a click to enter the conversation
user = driver.find_element_by_xpath("//span[@title = '{}']".format(name))
user.click()

while True:
   # in the conversation page, a span with title online is diplayed when user is online.
   #the web driver will wait 8hrs=28800s, if user not online all this time script will be killed by webdriverWait
   element = WebDriverWait(driver, 28800).until(
      EC.visibility_of_element_located(
         (By.XPATH, "//span[@title = 'online']")))

   #Moment the user came online
   now = datetime.datetime.now()
   print("online at : ")
   print(now.strftime("%H:%M:%S"))

   element = WebDriverWait(driver, 28800).until(
      EC.invisibility_of_element_located(
         (By.XPATH, "//span[@title = 'online']")))

   #Moment the user went offline
   now = datetime.datetime.now()
   print("offline at : ")
   print(now.strftime("%H:%M:%S"))
   print("************")