使用selenium python通过类名查找第n个元素

I just started using selenium yesterday to help scrape some data and I'm having a difficult time wrapping my head around the selector engine. I know lxml, BeautifulSoup, jQuery and Sizzle have similar engines. But what I'm trying to do is:

我昨天刚开始使用selenium来帮助收集一些数据，我很难在选择器引擎上下功夫。我知道lxml、BeautifulSoup、jQuery和Sizzle都有类似的引擎。但我想做的是:

Wait 10 seconds for page to completely load
等待10秒，页面才能完全加载
Make sure there are the presence of ten or more span.eN elements (two load on intitial page load and more after)
确保有10个或更多的跨度。eN元素(初始页面加载两个加载，之后加载更多)
Then start processing the data with beautifulsoup
然后开始用beautifulsoup处理数据

I am struggling with the selenium conditions of either finding the nth element or locating the specific text that only exists in an nth element. I keep getting errors (timeout, NoSuchElement, etc)

我正在为寻找第n个元素或定位仅存在于第n个元素中的特定文本的硒条件而苦恼。我不断收到错误(超时，NoSuchElement，等等)

    url = "http://someajaxiandomain.com/that-injects-html-after-pageload.aspx"
    wd = webdriver.Chrome()
    wd.implicitly_wait(10)
    wd.get(url)
    # what I've tried
    # .find_element_by_xpath("//span[@class='eN'][10]"))
    # .until(EC.text_to_be_present_in_element(By.CSS_SELECTOR, "css=span[class='eN']:contains('foo')"))

1 个解决方案

#1

You need to understand the concept of Explicit Waits and Expected Conditions to wait for.

您需要理解显式等待和预期条件的概念。

In your case, you can write a custom Expected Condition to wait for elements count found by a locator being equal to n:

在您的情况下，您可以编写一个自定义期望条件，等待定位器找到的元素计数为n:

from selenium.webdriver.support import expected_conditions as EC

class wait_for_n_elements_to_be_present(object):
    def __init__(self, locator, count):
        self.locator = locator
        self.count = count

    def __call__(self, driver):
        try:
            elements = EC._find_elements(driver, self.locator)
            return len(elements) >= self.count
        except StaleElementReferenceException:
            return False

Usage:

用法:

n = 10  # specify how many elements to wait for

wait = WebDriverWait(driver, 10)
wait.until(wait_for_n_elements_to_be_present((By.CSS_SELECTOR, 'span.eN'), n))

Probably, you could have also just used a built-in Expected Condition such as presence_of_element_located or visibility_of_element_located and wait for a single span.eN element to be present or visible, example:

可能，您还可以使用一个内置的预期条件，比如presence_of_element_locate或visibility_of_element_locate，然后等待一个span。要显示或可见的元素，例如:

wait = WebDriverWait(driver, 10)
wait.until(presence_of_element_located((By.CSS_SELECTOR, 'span.eN')))

#1