python - 为什么硒找不到标签和类
问题描述
我最近开始使用 selenium,但我无法解决一个问题。当我使用 find_element_by_tag(class)_name 或 _css_selector 引发错误时:
selenium.common.exceptions.NoSuchElementException: Message: no such element: Unable to locate element:
但我正在寻找的元素存在。
例如:
from selenium import webdriver
from webdriver_manager.chrome import ChromeDriverManager
browser = webdriver.Chrome(ChromeDriverManager().install())
url='http://inventwithpython.com/'
browser.get(url)
a = browser.find_element_by_class_name('navbar navbar-toggleable-md')
输出:
[WDM] - Current google-chrome version is 85.0.4183
[WDM] - Get LATEST driver version for 85.0.4183
[WDM] - Driver [C:\Users\vladv\.wdm\drivers\chromedriver\win32\85.0.4183.87\chromedriver.exe] found in cache
Traceback (most recent call last):
File "C:/Users/vladv/PycharmProjects/untitled1/черновик.py", line 14, in <module>
a = browser.find_element_by_class_name('navbar navbar-toggleable-md')
File "C:\Users\vladv\AppData\Local\Programs\Python\Python37\lib\site-packages\selenium\webdriver\remote\webdriver.py", line 564, in find_element_by_class_name
return self.find_element(by=By.CLASS_NAME, value=name)
File "C:\Users\vladv\AppData\Local\Programs\Python\Python37\lib\site-packages\selenium\webdriver\remote\webdriver.py", line 978, in find_element
'value': value})['value']
File "C:\Users\vladv\AppData\Local\Programs\Python\Python37\lib\site-packages\selenium\webdriver\remote\webdriver.py", line 321, in execute
self.error_handler.check_response(response)
File "C:\Users\vladv\AppData\Local\Programs\Python\Python37\lib\site-packages\selenium\webdriver\remote\errorhandler.py", line 242, in check_response
raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.NoSuchElementException: Message: no such element: Unable to locate element: {"method":"css selector","selector":".navbar navbar-toggleable-md"}
(Session info: chrome=85.0.4183.102)
但是如果我想找到“navbar-brand”类,我可以做到。有什么问题?
如果我使用 find_elements,则返回空列表。
PS如果有人可以建议一些有用的材料来研究硒,那将非常有帮助。
解决方案
根据selenium.webdriver.common.by
实施文档:
class selenium.webdriver.common.by.By
Set of supported locator strategies.
CLASS_NAME = 'class name'
因此,使用find_element_by_class_name()
您将无法传递多个类名。通过多个类,您将面临错误。
解决方案
要定位元素,您可以使用以下任一Locator Strategies:
使用
css_selector
:element = driver.find_element_by_css_selector("nav.navbar.navbar-toggleable-md")
使用
xpath
:element = driver.find_element_by_xpath("//nav[@class='navbar navbar-toggleable-md']")
理想情况下,要定位您需要诱导WebDriverWait的元素visibility_of_element_located()
,您可以使用以下任一Locator Strategies:
使用
CSS_SELECTOR
:element = WebDriverWait(driver, 20).until(EC.visibility_of_element_located((By.CSS_SELECTOR, "nav.navbar.navbar-toggleable-md")))
使用
XPATH
:element = WebDriverWait(driver, 20).until(EC.visibility_of_element_located((By.XPATH, "//nav[@class='navbar navbar-toggleable-md']")))
注意:您必须添加以下导入:
from selenium.webdriver.support.ui import WebDriverWait from selenium.webdriver.common.by import By from selenium.webdriver.support import expected_conditions as EC
参考
您可以在以下位置找到一些相关的详细讨论:
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