Selenium is not properly determining if a page has a html tag

问题

I'm trying to get Selenium to wait until the title tag of a web page is present when loading with Python.

I've tried testing this code with other types of HTML tags and only the <body> tag didn't result in an error.

wait = WebDriverWait(driver, 10)
driver.get(link)
wait.until(EC.visibility_of_element_located((By.TAG_NAME, 'div')))

I expected the code to evaluate to completion but I got the following error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.7/site-packages/selenium/webdriver/support/wait.py", line 80, in until
    raise TimeoutException(message, screen, stacktrace)
selenium.common.exceptions.TimeoutException: Message:

回答1:

The title tag is never visible. You can wait for its presence, though:

wait.until(EC.presence_of_element_located((By.TAG_NAME, 'title')))

The title also has its own expected conditions, title_is() and title_contains(). For example:

wait.until(EC.title_is("Google"))

You can review the complete list of supported expected conditions in the documentation.

回答2:

If you want to access the Page Title locating the <title> tag is not the ideal way.

To print the title you need to induce WebDriverWait either for either of the following expected_conditions:

title_contains(partial_title)
title_is(title)

An example:

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

options = webdriver.ChromeOptions() 
options.add_argument("start-maximized")
options.add_argument('disable-infobars')
driver = webdriver.Chrome(chrome_options=options, executable_path=r'C:\WebDrivers\chromedriver.exe')
driver.get("https://www.google.com/")
WebDriverWait(driver, 10).until(EC.title_contains("G"))
print("Page title is: %s" %(driver.title))