Python Selenium: Can't find element by xpath when browser is headless

Question

I'm attempting to log into a website using Python Selenium using the following code:

import time
from contextlib import contextmanager
from selenium import webdriver
from selenium.webdriver.chrome.options import Options

@contextmanager
def getBrowser(*options):
    chrome_options = Options()
    if options: [chrome_options.add_argument(option) for option in options]
    browser = webdriver.Chrome(chrome_options=chrome_options)
    try:
        yield browser
    finally:
        browser.quit()


with getBrowser() as browser:
    browser.get('https://www.vinted.com/members/notifications')

    time.sleep(20)
    browser.find_element_by_xpath('//*[@id="content"]/div/div[2]/div/div/div[6]/div[3]/div[3]/a/span').click()

It works perfectly, however when I add the --headless option to the browser, it raises a NoSuchElementException.

Error raising code:

with getBrowser('--headless') as browser:
    browser.get('https://www.vinted.com/members/notifications')

    time.sleep(20)
    browser.find_element_by_xpath('//*[@id="content"]/div/div[2]/div/div/div[6]/div[3]/div[3]/a/span').click()

Traceback:

Traceback (most recent call last):

  File "<ipython-input-4-fe0834deb137>", line 1, in <module>
    runfile('C:/Users/Alec/vinted test case.py', wdir='C:/Users/Alec')

  File "C:\Users\Alec\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 705, in runfile
    execfile(filename, namespace)

  File "C:\Users\Alec\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 102, in execfile
    exec(compile(f.read(), filename, 'exec'), namespace)

  File "C:/Users/Alec/vinted test case.py", line 27, in <module>
    browser.find_element_by_xpath('//*[@id="content"]/div/div[2]/div/div/div[6]/div[3]/div[3]/a/span').click()

  File "C:\Users\Alec\selenium\webdriver\remote\webdriver.py", line 354, in find_element_by_xpath
    return self.find_element(by=By.XPATH, value=xpath)

  File "C:\Users\Alec\selenium\webdriver\remote\webdriver.py", line 832, in find_element
    'value': value})['value']

  File "C:\Users\Alec\selenium\webdriver\remote\webdriver.py", line 297, in execute
    self.error_handler.check_response(response)

  File "C:\Users\Alec\selenium\webdriver\remote\errorhandler.py", line 194, in check_response
    raise exception_class(message, screen, stacktrace)

NoSuchElementException: no such element: Unable to locate element: {"method":"xpath","selector":"//*[@id="content"]/div/div[2]/div/div/div[6]/div[3]/div[3]/a/span"}
  (Session info: headless chrome=65.0.3325.181)
  (Driver info: chromedriver=2.36.540470 (e522d04694c7ebea4ba8821272dbef4f9b818c91),platform=Windows NT 10.0.16299 x86_64)

This error only occurs when the browser is headless. What's causing this behavior? Can it be made to work in headless mode?

target HTML:

<div class="u-flex-grow">
      <a class="c-button--inverse c-button--normal c-button--amplified c-button " href="/member/general/login?ref_url=%2Fmembers%2Fnotifications"><span class="c-button__content">Log In</span></a>
    </div>

Answer 1

I had once some trouble with the versions of such tools. I fixed that by ensuring I had the latest version of Chrome and webdriver installed. Maybe it's a similar issue?!

But apart of that your selector depends on a lot elements. So imagining that the html looks a bit different in headless mode could lead to your issue.

I would try to get a less strict selector like the following: //a[starts-with(@href,'/member/general/login?')]

If that is not working try to dump the html into a file from within the headless mode. Just to see what the headless browser sees and trying build a fancy selector with that.