html - StaleElementReferenceException on Python Selenium

Question

I am getting the following error while using Selenium in python:

selenium.common.exceptions.StaleElementReferenceException: Message: u'stale element reference: element is not attached to the page document\n

Interestingly enough, the error pops up at different times in the for loop. Sometimes it gets through eg. 4 iterations and other times eg. 7.

Some of the relevant code being run is:

for i in range(0, 22):
    u = driver.find_elements_by_id("data")
    text = u[0].get_attribute("innerHTML")
    driver.find_elements_by_class_name("aclassname")[0].click()

What does this error mean and what is something I can try to fix this?

Answer 1

It means the element is no longer in the DOM, or it changed.

The following code will help you find the element by controlling and ignoring StaleElementExceptions and handling them just like any other NoSuchElementException. It waits for the element to NOT be stale, just like it waits for the element to be present. It also serves as a good example on how to properly wait for conditions in Selenium.

from selenium.common.exceptions import NoSuchElementException
from selenium.common.exceptions import StaleElementReferenceException
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions

my_element_id = 'something123'
ignored_exceptions=(NoSuchElementException,StaleElementReferenceException,)
your_element = WebDriverWait(your_driver, some_timeout,ignored_exceptions=ignored_exceptions)\
                        .until(expected_conditions.presence_of_element_located((By.ID, my_element_id)))

To better understand the problem, imagine you are inside a for loop and think what happens during the iterations:

1. something changes when you click on the element (last line)
2. So the page is changing
3. You enter the next iteration. Now are trying to find a new element (your first line inside the loop).
4. You found the element
5. It finishes changing
6. You try to use it by getting an attribute
7. Bam! The element is old. You got it in step 4, but it finished changing on step 5

Answer 2

Selenium Support Explicit and Implicit Waits. If you think waiting for certain amount of time is enough for your page to be loaded, use:

driver.implicitly_wait(secs)

but if you want to wait for a special event (e.g. waiting for a particular element to be loaded) you can do something like:

from selenium.webdriver.support.ui import WebDriverWait
...
...
def find(driver):
    element = driver.find_elements_by_id("data")
    if element:
        return element
    else:
        return False
element = WebDriverWait(driver, secs).until(find)

Answer 3

Beyond the answers here, if you are using ActionChains, and the page has changed, be sure to reinstantiate your ActionChains object (dont reuse an old one), otherwise your ActionChain will be using a stale DOM. I.e. do this;

action_chain = ActionChains(driver)     
action_chain.double_click(driver.find_element_by_xpath("//tr[2]/p")).perform()

Or better yet dont use an instantiation;

ActionChains(driver).double_click(driver.find_element_by_xpath("//tr[2]/p")).perform()

Answer 4

>>>Stale Exceptions can be handled using **StaleElementReferenceException** to continue the for loop execution.  

from selenium.common import exceptions  

# and customize your code of for loop as:  

for i in range(0, 22):  
   try:  
        u = driver.find_elements_by_id("data")  
        text = u[0].get_attribute("innerHTML")  
        driver.find_elements_by_class_name("aclassname")[0].click()  
   except exceptions.StaleElementReferenceException,e:
        print(e)
        pass  

Note: Python 3+ : replace exceptions.StaleElementReferenceException,e -> exceptions.StaleElementReferenceException as e

Answer 5

For my python scripts, on quite simple pages, all above mentioned solutions didn't work. I found here -> https://www.softwaretestingmaterial.com/stale-element-reference-exception-selenium-webdriver/ the simplest way for my problem. It's just refreshing before clicking.

driver.refresh()
driver.find_element_by_id('normal').click()

Note: I'm using driver.implicitly_wait(5) instead of explicit waits but it works in both options.

Answer 6

When webpage got refreshed or switched back from different window or form and trying to access an element user will get staleelementexception.

Use webdriverwait in try --except block with for loop: EX :

Code in which I got staleelementexception :

---

driver.find_element_by_id(tc.value).click()

driver.find_element_by_xpath("xpath").click()

---

Fix :

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

driver.find_element_by_id(tc.value).click()
for i in range(4):
   try:
        run_test = WebDriverWait(driver, 120).until( \
        EC.presence_of_element_located((By.XPATH, "xpath")))
        run_test.click()
        break
   except StaleElementReferenceException as e:
        raise e

Answer 7

I Would like to add one more solution here which is worked for me.

I was trying to access the button in the top menu panel on my webpage after refreshing the content area on the same page, Which gave me the following error,

    raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.StaleElementReferenceException: Message: The element reference of <span id="dk1-combobox" class="dk-selected combinationText visibleElements "> is stale; either the element is no longer attached to the DOM, it is not in the current frame context, or the document has been refreshed

Then I started to search for the solution to click the stale element on the web page. After two days of thinking and googling, I got a solution.

To access the stale element on the page, first, we need to focus the mouse over the particular section and perform click option

EditReport1 = driver.find_element_by_id('internalTab1')
ActionChains(driver).move_to_element(EditReport1).click(EditReport1).perform()

move_to_element will move the mouse over the stale element which we need to access once we got our control on the element the click operation is successfully performed.

This is worked for me. If anyone finds it working please comment your's as well which will help some other in future.

Thank you

Answer 8

In my case, the problem

stale element reference: element is not attached to the page document

was because I tried to use actions.move_to_element(element).perform() on actions that created from old Selenium tab.

So the solution is to create new actions instance after opening new tab:

actions = ActionChains(browser)
actions.move_to_element(element).perform()

Answer 9

This is the python solution for this problem:

def clickAndCatchStaleRefException(locator):



    driver = sel2._current_browser()
    result = False
    attempts = 0

    locator = locator[6:]
    # This line is optional because sometimes you pass a xpath from a varibles file
    # that starts with 'xpath='. This should be omitted otherwise the find_element_by_xpath 
    # function will throw an error.
    # But if you pass an xpath directly you don't need this


    while attempts < 2:
        try:
            driver.find_element_by_xpath(locator).click()
            result = True
            break
        except EC as e:
            raise e
        finally:
            attempts += 1
    return result

Answer 10

from selenium.webdriver.support.expected_conditions import staleness_of

Import above saved the day for me.

Answer 11

It depends on the Website you are working with.

If you have a Website, that doesn't change itself, use Emilio's answer. WebDriverWait(...).until(...) is the correct / best solution for Websites, that don't change by themselves (and only by user interactions):

WebDriverWait(driver, delay, ignored_exceptions=(NoSuchElementException,StaleElementReferenceException)).until(expected_conditions.presence_of_element_located((By.ID, "my_id"))).click()

(For explanation see Emilio's answer)

If you work with a site, that changes by pushs from server or time based or something similar, the only working solution is retrying like in Rashids answer.

def retry_func(func, max_tries=MAX_TRIES):
    for i in range(max_tries):
        try:
            return func()
        except Exception as e:
            if i >= max_tries - 1:
                raise e


def click_button_helper(driver, selector, selector_type=By.XPATH, delay=DELAY, ignored_exceptions=IGNORED_EXCEPTIONS):
    WebDriverWait(driver, delay, ignored_exceptions=ignored_exceptions).until(
        EC.presence_of_element_located((selector_type, selector))).click()


def click_button(driver, selector, selector_type=By.XPATH, delay=DELAY, ignored_exceptions=IGNORED_EXCEPTIONS,
                 max_tries=MAX_TRIES):
    retry_func(lambda: click_button_helper(driver, selector, selector_type, delay, ignored_exceptions), max_tries)

Because, sorry @Emilio, your answer doesn't address specific cases like the one Sylvan LE DEUNFF mentioned.

The following race condition is still possible (and not solved by WebDriverWait(...).until(...), but usually by retrying):

1. The page is changing (e.g. after a click like in the question)
2. We are trying to find the element.
3. WebDriverWait(...).until(...) waits for us till our expected_conditions are fullfilled (so basically till it finishes changing)
4. We found the element
5. It starts changing again (by push, by reaching timestep, ...)
6. We try to use it
7. Bam! The element is old again.

Answer 12

One scenario in my case : I queryed the element once , and assign it to an variable for reusage,

captchaInput = driver.find_element_by_css_selector('input[name="CaptchaCode"]')

then it runs the risk of StaleElementReferenceException, querying the element again with the above code help eliminate the exception.