使用 Python 迭代时出现 StaleElementException

Question

我正在尝试为亚马逊搜索结果创建一个基本的网络爬虫。当我遍历结果时，我有时会到达结果的第 5 页（有时只有第 2 页），然后抛出 StaleElementException。当我在抛出异常后查看浏览器时，我可以看到驱动程序/页面没有向下滚动到页码所在的位置（底部栏）。

我的代码：

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')

我看过这个question，我猜可以应用类似的修复，但我不确定如何在页面上找到消失的东西。此外，根据打印语句的发生速度，我可以看到 implicitly_wait(10) 实际上并没有等待整整 10 秒。

异常指向以“driver.execute_script”开头的行。这是一个例外：

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

有时我会收到 ValueError：

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

所以这些错误/异常让我相信等待页面完全刷新是有问题的。

Answer 1

如果您只想让脚本遍历所有结果页面，则不需要任何复杂的逻辑 - 只需在可能的情况下单击“下一步”按钮即可：

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

附：另请注意，implicitly_wait(10) 不应等待整整 10 秒，而是等待最多 10 秒以使元素出现在 HTML DOM 中。因此，如果在 1 或 2 秒内找到元素，则等待完成，您将不会等待休息 8-9 秒...

Answer 2

此错误消息...

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

...暗示该元素的先前引用现在已过时，并且该元素引用不再存在于页面的 DOM 上。

此问题背后的常见原因是：

• 元素在 HTML 中的位置发生了变化。
• 元素不再附加到 DOM 树。
• 元素所在的网页已刷新。
• 之前的元素实例已被 JavaScript 或 AjaxCall 刷新。

---

这个用例

通过scrollIntoView() 和打印 保留您的滚动 一些有用的调试消息的概念，我做了一些小的调整以诱导WebDriverWait您可以使用以下解决方案：

• 代码块：

  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()
  

• 控制台输出：

  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