Python Selenium 网络驱动程序。写我自己的预期条件

Question

我正在尝试编写我自己的预期条件。我需要什么...我有一个 iframe。我也有一张图片。当图像的 scr 发生变化时，我想继续处理。我做了什么:

class url_changed_condition(object):
    '''
    Checks whether url in iframe has changed or not
    '''
    def __init__(self, urls):
        self._current_url, self._new_url = urls

    def __call__(self, ignored):
        return self._current_url != self._new_url  

后来在我的代码中:

def process_image(self, locator, current_url):
    try:
        WebDriverWait(self.driver, 10).until(ec.presence_of_element_located((By.TAG_NAME, u"iframe")))
        iframe = self.driver.find_element(*locator)
        if iframe:
            print "Iframe found!"
        self.driver.switch_to_frame(iframe)
        WebDriverWait(self.driver, 10).until(ec.presence_of_element_located((By.XPATH, u"//div")))

        # WebDriverWait(self.driver, 10).until(
            # url_changed_condition(
                # (current_url, self.driver.find_element(By.XPATH, u"//a/img").get_attribute(u"src"))))

        img_url = self.driver.find_element(By.XPATH, u"//a/img").get_attribute(u"src")
        print img_url
        self.search_dict[self._search_item].append(img_url)
        self.driver.switch_to_default_content()
    except NoSuchElementException as NSE:
        print "iframe not found! {0}".format(NSE.msg)
    except:
        print "something went wrong"
        import traceback
        import sys
        type_, value_, trace_ = sys.exc_info()
        print type_, value_
        print traceback.format_tb(trace_)
    finally:
        return current_url  

此代码有效，但多次返回相同的 url。问题是当我取消注释 url_changed_condition 时，它会在
中出现 TimeoutException(current_url, self.driver.find_element(By.XPATH, u"//a/img").get_attribute(u"src"))
它下面的行工作正常...我不明白。

Answer 1

此主题似乎缺少自定义预期条件的示例。

其实很简单。首先，什么是Expected Condition in Python selenium bindings :

• 它是一个新式class(基于object)
• 它有 __call__() magic method defined它返回一个 bool 值

有一大套built-in expected condition classes .

让我们通过示例来工作。假设我们想要等到元素的文本以所需文本开头:

from selenium.webdriver.support import expected_conditions as EC

class wait_for_text_to_start_with(object):
    def __init__(self, locator, text_):
        self.locator = locator
        self.text = text_

    def __call__(self, driver):
        try:
            element_text = EC._find_element(driver, self.locator).text
            return element_text.startswith(self.text)
        except StaleElementReferenceException:
            return False

用法:

WebDriverWait(driver, 10).until(wait_for_text_to_start_with((By.ID, 'myid'), "Hello, World!"))