StaleElementException when iterating with Python

问题:

I'm trying to create a basic web scraper for Amazon results. As I'm iterating through results, I sometimes get to page 5 (sometimes only page 2) of the results and then a StaleElementException is thrown. When I look at the browser after the exception is thrown, I can see that the driver/page did not scroll down to where the page numbers are (bottom bar).

My code:

driver.get('https://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias%3Daps&field-keywords=sonicare+toothbrush')

for page in range(1,last_page_number +1):

    driver.implicitly_wait(10)

    bottom_bar = driver.find_element_by_class_name('pagnCur')
    driver.execute_script("arguments[0].scrollIntoView(true);", bottom_bar)

    current_page_number = int(driver.find_element_by_class_name('pagnCur').text)

    if page == current_page_number:
        next_page = driver.find_element_by_xpath('//div[@id="pagn"]/span[@class="pagnLink"]/a[text()="{0}"]'.format(current_page_number+1))
        next_page.click()
        print('page #',page,': going to next page')
    else:
        print('page #: ', page,'error')

I've looked at this question, and I'm guessing that a similar fix can be applied, but I'm not sure how to find something on the page that disappears. Also, based on how quickly the print statements are occurring, I can see that the implicitly_wait(10) isn't actually waiting a full 10 seconds.

The exception is pointing to the line that starts with "driver.execute_script". This is the exception:

StaleElementReferenceException: Message: The element reference of <span class="pagnCur"> 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

Sometimes I'll get a ValueError:

ValueError: invalid literal for int() with base 10: ''

So these errors/exceptions lead me to believe that there is something going on with waiting for the page to refresh completely.

回答1:

If you just want your script to iterate over all the result pages, you don't need any complicated logic - just make a click on Next button while it's possible:

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

driver = webdriver.Chrome()

driver.get('https://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias%3Daps&field-keywords=sonicare+toothbrush')

while True:
    try:
        wait(driver, 10).until(EC.element_to_be_clickable((By.CSS_SELECTOR, 'a > span#pagnNextString'))).click()
    except TimeoutException:
        break

P.S. Also note that implicitly_wait(10) should not wait full 10 seconds, but wait up to 10 seconds for element to appear in HTML DOM. So if element is found within 1 or 2 seconds then wait is done and you will not wait rest 8-9 seconds...

回答2:

It seems you were almost there.

Preserving your concept of scrolling through scrollIntoView() and printing a couple of helpful debug messages, I have made some minor adjustments inducing WebDriverWait and you can use the following solution:

• Code Block:

  from selenium import webdriver
  from selenium.webdriver.chrome.options import Options
  from selenium.webdriver.common.by import By
  from selenium.webdriver.support.ui import WebDriverWait
  from selenium.webdriver.support import expected_conditions as EC
  
  options = Options()
  options.add_argument("start-maximized")
  options.add_argument('disable-infobars')
  options.add_argument("--disable-extensions")
  driver = webdriver.Chrome(chrome_options=options, executable_path=r'C:\Utility\BrowserDrivers\chromedriver.exe')
  driver.get("https://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias%3Daps&field-keywords=sonicare+toothbrush")
  while True:
      try:
          current_page_number_element = WebDriverWait(driver, 20).until(EC.visibility_of_element_located((By.CSS_SELECTOR, "span.pagnCur")))
          driver.execute_script("arguments[0].scrollIntoView(true);", current_page_number_element)
          current_page_number = current_page_number_element.get_attribute("innerHTML")
          WebDriverWait(driver, 10).until(EC.element_to_be_clickable((By.CSS_SELECTOR, "span.pagnNextArrow"))).click()
          print("page # {} : going to next page".format(current_page_number))
      except:
          print("page # {} : error, no more pages".format(current_page_number))
          break
  driver.quit()
  

• Console Output:

  page # 1 : going to next page
  page # 2 : going to next page
  page # 3 : going to next page
  page # 4 : going to next page
  page # 5 : going to next page
  page # 6 : going to next page
  page # 7 : going to next page
  page # 8 : going to next page
  page # 9 : going to next page
  page # 10 : going to next page
  page # 11 : going to next page
  page # 12 : going to next page
  page # 13 : going to next page
  page # 14 : going to next page
  page # 15 : going to next page
  page # 16 : going to next page
  page # 17 : going to next page
  page # 18 : going to next page
  page # 19 : going to next page
  page # 20 : error, no more pages