StaleElementReferenceException on Python Selenium

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?

Solution 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

Solution 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)

Solution 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()

Solution 4:

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.

Solution 5:

>>>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