Python 使用classname、css选择器和xpath从网站查找元素

我正在寻找代码方面的帮助

我试图从一个网站打印出一个元素，但是我从我尝试的方法中得到了不同的错误消息，它们都不起作用

我已尝试将class_name与以下代码一起使用：

from selenium import webdriver    
browser = webdriver.Chrome('/home/cena/Downloads/chromedriver')

poeisz_url = "https://webwinkel.poiesz-supermarkten.nl/boodschappen/producten/631258"
poeisz_classname = "full-product full-product--price__for"

browser.get(poeisz_url)
elem = browser.find_element_by_class_name(poeisz_classname)
print(elem.text)

这返回了以下错误消息：

Traceback (most recent call last):
  File "/home/cena/.PyCharmCE2019.1/config/scratches/scratch_2.py", line 9, in <module>
    elem = browser.find_element_by_class_name(poeisz_classname)
  File "/usr/local/lib/python3.7/dist-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 "/usr/local/lib/python3.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 978, in find_element
    'value': value})['value']
  File "/usr/local/lib/python3.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 321, in execute
    self.error_handler.check_response(response)
  File "/usr/local/lib/python3.7/dist-packages/selenium/webdriver/remote/errorhandler.py", line 242, in check_response
    raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.InvalidSelectorException: Message: invalid selector: Compound class names not permitted
  (Session info: chrome=74.0.3729.169)
  (Driver info: chromedriver=74.0.3729.6 (255758eccf3d244491b8a1317aa76e1ce10d57e9-refs/branch-heads/3729@{#29}),platform=Linux 4.15.0-50-generic x86_64)

他们依次返回了以下错误：

Traceback (most recent call last):
  File "/home/cena/.PyCharmCE2019.1/config/scratches/scratch_2.py", line 9, in <module>
    elem = browser.find_element_by_xpath("//*[@class='" + poeisz_classname + "']")
  File "/usr/local/lib/python3.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 394, in find_element_by_xpath
    return self.find_element(by=By.XPATH, value=xpath)
  File "/usr/local/lib/python3.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 978, in find_element
    'value': value})['value']
  File "/usr/local/lib/python3.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 321, in execute
    self.error_handler.check_response(response)
  File "/usr/local/lib/python3.7/dist-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":"xpath","selector":"//*[@class='full-product full-product--price__for']"}
  (Session info: chrome=74.0.3729.169)
  (Driver info: chromedriver=74.0.3729.6 (255758eccf3d244491b8a1317aa76e1ce10d57e9-refs/branch-heads/3729@{#29}),platform=Linux 4.15.0-50-generic x86_64)

回溯（最近一次呼叫最后一次）：
文件“/home/cena/.PyCharmCE2019.1/config/scratch/scratch_2.py”，第9行，在
elem=browser。通过xpath（“/*[@class=”+poeisz\u classname+“]”）查找元素
文件“/usr/local/lib/python3.7/dist-packages/selenium/webdriver/remote/webdriver.py”，第394行，按xpath查找元素
返回self.find_元素（by=by.XPATH，value=XPATH）
文件“/usr/local/lib/python3.7/dist packages/selenium/webdriver/remote/webdriver.py”，第978行，在find_元素中
'value'：value}）['value']
文件“/usr/local/lib/python3.7/dist-packages/selenium/webdriver/remote/webdriver.py”，执行中第321行
self.error\u handler.check\u响应（响应）
文件“/usr/local/lib/python3.7/dist packages/selenium/webdriver/remote/errorhandler.py”，第242行，在check_响应中
引发异常类（消息、屏幕、堆栈跟踪）
selenium.common.exceptions.NoSuchElementException:消息：没有这样的元素：无法定位元素：{“方法”：“xpath”，“选择器”：“/*[@class='full-product full-product-product--price_for']”}
（会话信息：chrome=74.0.3729.169）
（驱动程序信息：chromedriver=74.0.3729.6（255758ECCF3D24491B8A1317AA76E1CE10D57E9参考/分支头/3729{29}），平台=Linux 4.15.0-50-generic x86_64）

回溯（最近一次呼叫最后一次）：
文件“/home/cena/.PyCharmCE2019.1/config/scratch/scratch_2.py”，第9行，在
elem=browser。通过css选择器（“*[class^=”+poeisz\u classname+“]”）查找元素
文件“/usr/local/lib/python3.7/dist packages/selenium/webdriver/remote/webdriver.py”，第598行，按css选择器查找元素
返回self.find_元素（by=by.CSS_选择器，value=CSS_选择器）
文件“/usr/local/lib/python3.7/dist packages/selenium/webdriver/remote/webdriver.py”，第978行，在find_元素中
'value'：value}）['value']
文件“/usr/local/lib/python3.7/dist-packages/selenium/webdriver/remote/webdriver.py”，执行中第321行
self.error\u handler.check\u响应（响应）
文件“/usr/local/lib/python3.7/dist packages/selenium/webdriver/remote/errorhandler.py”，第242行，在check_响应中
引发异常类（消息、屏幕、堆栈跟踪）
selenium.common.exceptions.NoSuchElementException:消息：没有这样的元素：无法找到元素：{“方法”：“css选择器”，“选择器”：“*[class^='full-product full-product-price_for']”
（会话信息：chrome=74.0.3729.169）
（驱动程序信息：chromedriver=74.0.3729.6（255758ECCF3D24491B8A1317AA76E1CE10D57E9参考/分支头/3729{29}），平台=Linux 4.15.0-50-generic x86_64）

我对编程很陌生，所以如果这是件愚蠢的事情，我很抱歉。提前感谢您的帮助

您应该使用：

例如XPath：

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC


driver = webdriver.Chrome('/home/cena/Downloads/chromedriver')
url = "https://webwinkel.poiesz-supermarkten.nl/boodschappen/producten/631258"
driver.get(url)
my_el = WebDriverWait(driver, 20).until(EC.presence_of_element_located((By.XPATH, '//div[@id="products"]//*[@class="full-product full-product--price__for"]')))
print(my_el.text)

输出为：

0 99

使用

WebDriverWait

的更好方法是将其用作变量：

wait = WebDriverWait(driver, 20)
my_el = wait.until(EC.presence_of_element_located((By.XPATH, '//div[@id="products"]//*[@class="full-product full-product--price__for"]')))

如前所述，您可能希望使用位于的元素的可见性（）而不是位于的元素的存在性

---

希望这对你有帮助

第一条错误消息解释了您遇到的问题

选择器无效：不允许使用复合类名

find_element_by_class_name（）

采用单个类名作为参数，但“完整产品-完整产品-价格-价格”包含两个类名（注意：类名用空格分隔，所以这里有两个…“完整产品”和“完整产品-价格-价格-价格”

您可以将定位器转换为CSS选择器，

.full product.full product--

的price\u，它应该可以正常工作

要阅读有关CSS选择器的更多信息，请参阅下面的链接

---

如果您不介意我问一下，为什么这样做？对不起，我没有太多经验：）基本思想是显式地等待一个元素。。。发生的情况是，有时您的驱动程序运行速度很快，但元素尚未加载。。。这是使用显式等待而不是睡眠的最佳实践。。。

Traceback (most recent call last):
  File "/home/cena/.PyCharmCE2019.1/config/scratches/scratch_2.py", line 9, in <module>
    elem = browser.find_element_by_css_selector("*[class^='" + poeisz_classname + "']")
  File "/usr/local/lib/python3.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 598, in find_element_by_css_selector
    return self.find_element(by=By.CSS_SELECTOR, value=css_selector)
  File "/usr/local/lib/python3.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 978, in find_element
    'value': value})['value']
  File "/usr/local/lib/python3.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 321, in execute
    self.error_handler.check_response(response)
  File "/usr/local/lib/python3.7/dist-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":"*[class^='full-product full-product--price__for']"}
  (Session info: chrome=74.0.3729.169)
  (Driver info: chromedriver=74.0.3729.6 (255758eccf3d244491b8a1317aa76e1ce10d57e9-refs/branch-heads/3729@{#29}),platform=Linux 4.15.0-50-generic x86_64)

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC


driver = webdriver.Chrome('/home/cena/Downloads/chromedriver')
url = "https://webwinkel.poiesz-supermarkten.nl/boodschappen/producten/631258"
driver.get(url)
my_el = WebDriverWait(driver, 20).until(EC.presence_of_element_located((By.XPATH, '//div[@id="products"]//*[@class="full-product full-product--price__for"]')))
print(my_el.text)

wait = WebDriverWait(driver, 20)
my_el = wait.until(EC.presence_of_element_located((By.XPATH, '//div[@id="products"]//*[@class="full-product full-product--price__for"]')))