Python, Selenium find element with class and wait for class change

问题

I have a web page which loads content dynamically and while page loads, there is spinning wheel, I already found solution to grab content loaded immediately on page, but seems i can't find solution to grab content loaded later in dom.

What i can think of is to find element with specific class of that wheel spinning, and wait for it to change, once it's changed, than it means content is loaded in dom.

I am using Selenium with Firefox webdriver on Ubuntu.

Here is the class i am looking to monitor:

<div class="wheel spinning"></div>

Once content is loaded, wheel stop spinning and class is changed to:

<div class="wheel"></div>

Anyone find solution to find and monitor class="wheel spinning" and once it's changed to class="wheel" to continue to grab data.

Edit:

The XPATH actually solved one part of solution, here's part of code

try:
    element = WebDriverWait(driver, 10).until(
EC.presence_of_element_located((By.XPATH, "//*[@class='wheel']))
)
title = driver.find_element_by_xpath('/html/body/div[1]/div[1]/div[3]')
print(title.text)

But if element don't appear within 10 seconds it error's out, now to find a way to retry again and again until element is present on page.

Is there a difference in use presence_of_element_located((By.XPATH)) and find_element_by_xpath

回答1:

@LucasTierney's answer was in the right direction. However I still feel the solution can be optimized as follows:

As the wheel is visible, instead of presence_of_element_located() method you need to use visibility_of_element_located() method.

The node:

<div class="wheel spinning"></div>

Can't be located through the XPath containing a single class i.e. only wheel as in:

el = WebDriverWait(driver, 30).until(EC.presence_of_element_located((By.XPATH, "//*[@class='wheel']")))

Instead you can use either of the Locator Strategies:

• cssSelector:

  el = WebDriverWait(driver, 30).until(EC.visibility_of_element_located((By.CSS_SELECTOR, "div.wheel.spinning")))
  WebDriverWait(driver, 10).until(lambda d: 'spinning' not in el.get_attribute('class'))
  

• xpath:

  el = WebDriverWait(driver, 30).until(EC.visibility_of_element_located((By.XPATH, "//div[@class='wheel spinning']")))
  WebDriverWait(driver, 10).until(lambda d: 'spinning' not in el.get_attribute('class'))
  

回答2:

You can wait for the class value to change. For example:

from selenium.webdriver.support.ui import WebDriverWait

# Wait longer than 10 seconds since you're getting occasional timeout
el = WebDriverWait(driver, 30).until(EC.presence_of_element_located((By.XPATH, "//*[@class='wheel']")))


wait = WebDriverWait(driver, 10)
wait.until(lambda d: 'spinning' not in el.get_attribute('class'))

The until method passes the driver to the method given, so you can make your own expected condition pretty easily. The above uses an anonymous lambda function but you could also use a closure or a anything callable that takes in an argument (the ExpectedConditions library is just a set of callable classes). Here is the same with a closure:

from selenium.webdriver.support.ui import WebDriverWait


# Wait longer than 10 seconds since you're getting occasional timeout
el = WebDriverWait(driver, 30).until(EC.presence_of_element_located((By.XPATH, "//*[@class='wheel']")))

def wait_not_spinning(driver):
    return 'spinning' not in el.get_attribute('class')

wait = WebDriverWait(driver, 10)
wait.until(wait_not_spinning)

来源：https://stackoverflow.com/questions/53240157/python-selenium-find-element-with-class-and-wait-for-class-change