Python爬虫系列-Selenium详解
自动化测试工具,支持多种浏览器。爬虫中主要用来解决JavaScript渲染的问题。
用法讲解
模拟百度搜索网站过程:
from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.common.keys import Keys
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.support.wait import WebDriverWait
browser = webdriver.Chrome() # 声明浏览器对象
try:
browser.get('https://www.baidu.com')
input = browser.find_element_by_id('kw')
input.send_keys('Python')
input.send_keys(Keys.ENTER)
wait = WebDriverWait(browser,10)
wait.until(EC.presence_of_element_located((By.ID,'content_left')))
print(browser.current_url)
print(browser.get_cookies())
print(browser.page_source())
finally:
browser.close()
声明浏览器对象
from selenium import webdriver
browser = webdriver.Chrome()
browser = webdriver.Firefox()
browser = webdriver.Safari()
访问页面
from selenium import webdriver
browser = webdriver.Chrome()
browser.get('https://www.taobao.com')
print(browser.page_source)
browser.close()
~
查找元素
单个元素
from selenium import webdriver
browser = webdriver.Chrome()
browser.get('https://www.taobao.com')
input_first = browser.find_element_by_id('q')
input_second = browser.find_element_by_css_selector('#q')
input_third = browser.find_element_by_xpath('//*[@id="q"]')
print(input_first,input_second,input_third)
browser.close()
输出结果:
<selenium.webdriver.remote.webelement.WebElement (session="5871542b8137fd6a37c24e8ceb6ca644", element="0.26013942424402736-1")>
<selenium.webdriver.remote.webelement.WebElement (session="5871542b8137fd6a37c24e8ceb6ca644", element="0.26013942424402736-1")>
<selenium.webdriver.remote.webelement.WebElement (session="5871542b8137fd6a37c24e8ceb6ca644", element="0.26013942424402736-1")>
常用的一些方法:
- find_element_by_name
- find_element_by_xpath
- find_element_by_link_text
- find_element_by_partial_link_text
- find_element_by_tag_name
- find_element_by_class_name
- find_element_by_css_selector
from selenium import webdriver
from selenium.webdriver.common.by import By
browser = webdriver.Chrome()
browser.get('https://www.taobao.com')
input_third = browser.find_element(By.ID,'q')
print(input_third)
browser.close()
<selenium.webdriver.remote.webelement.WebElement (session="022c5603607ebd3b1268c4e4f776be87", element="0.07727375735629027-1")>
多个元素
element变为elements,其他没变化
from selenium import webdriver
browser = webdriver.Chrome()
browser.get('https://www.taobao.com')
lis = browser.find_elements_by_css_selector('.service-bd li')
print(lis)
browser.close()
from selenium import webdriver
from selenium.webdriver.common.by import By
browser = webdriver.Chrome()
browser.get('https://www.taobao.com')
lis = browser.find_elements(By.CSS_SELECTOR,'.service-bd li')
print(lis)
browser.close()
常用的一些方法:
- find_elements_by_name
- find_elements_by_xpath
- find_elements_by_link_text
- find_elements_by_partial_link_text
- find_elements_by_tag_name
- find_elements_by_class_name
- find_elements_by_css_selector
元素交互操作
对获取的元素调用交互方法
from selenium import webdriver
import time
browser = webdriver.Chrome()
browser.get('https://www.taobao.com')
input = browser.find_element_by_id('q')
input.send_keys('iPhone')
time.sleep(1)
input.clear()
input.send_keys('iPad')
button = browser.find_element_by_class_name('btn-search')
button.click()
交互动作
将动作附加到动作链中串行执行
from selenium import webdriver
from selenium.webdriver import ActionChains
browser = webdriver.Chrome()
url = 'http://www.runoob.com/try/try.php?filename=jqueryui-api-droppable'
browser.get(url)
browser.switch_to.frame('iframeResult')
source = browser.find_element_by_css_selector('#draggable')
target = browser.find_element_by_css_selector('#droppable')
actions = ActionChains(browser)
actions.drag_and_drop(source,target)
actions.perform()
执行JavaScript操作
把知乎拉到最下面:
from selenium import webdriver
browser = webdriver.Chrome()
browser.get('https://www.zhihu.com/explore')
browser.execute_script('window.scrollTo(0,document.body.scrollHeight)')
browser.execute_script('alert("To Bottom")')
获取元素信息
获取属性
from selenium import webdriver
from selenium.webdriver import ActionChains
browser = webdriver.Chrome()
url = 'https://www.zhihu.com/explore'
browser.get(url)
logo = browser.find_element_by_id('zh-top-link-logo')
print(logo)
print(logo.get_attribute('class'))
<selenium.webdriver.remote.webelement.WebElement (session="d35b5df5c39c24aae9b503846031b648", element="0.12337107958017368-1")>
zu-top-link-logo
获取文本值
from selenium import webdriver
browser = webdriver.Chrome()
url = 'https://www.zhihu.com/explore'
browser.get(url)
i = browser.find_element_by_class_name('zu-top-add-question')
print(i.text)
browser.close()
提问
获取ID、位置、标签名、大小
from selenium import webdriver
browser = webdriver.Chrome()
url = 'https://www.zhihu.com/explore'
browser.get(url)
i = browser.find_element_by_class_name('zu-top-add-question')
print(i.id)
print(i.location)
print(i.tag_name)
print(i.size)
browser.close()
0.25584226320534253-1
{'x': 651, 'y': 7}
button
Frame
在子Frame里面无法查找父Frame里面的元素:
import time
from selenium import webdriver
from selenium.common.exceptions import NoSuchElementException
browser = webdriver.Chrome()
url = 'http://www.runoob.com/try/try.php?filename=jqueryui-api-droppable'
browser.get(url)
browser.switch_to.frame('iframeResult')
source = browser.find_element_by_css_selector('#draggable')
print(source)
try:
logo = browser.find_element_by_class_name('logo')
except NoSuchElementException:
print('No Logo')
browser.switch_to.parent_frame()
logo = browser.find_element_by_class_name('logo')
print(logo)
print(logo.text)
显示如下:
<selenium.webdriver.remote.webelement.WebElement (session="a1e6dba0e8fba300e4c57efaed1734ac", element="0.5033848821354301-1")>
No Logo
<selenium.webdriver.remote.webelement.WebElement (session="a1e6dba0e8fba300e4c57efaed1734ac", element="0.7358889613858988-2")>
RUNOOB.COM
等待
隐式等待
当使用了隐式等待执行测试的时候,如果WebDriver没有在DOM中找到元素,将继续等待,超出设定时间后则抛出找不到元素的异常,换句话说,当查找元素或元素并没有立即出现的时候,隐式等待将等待一段时间再查找DOM,默认时间是0
from selenium import webdriver
browser = webdriver.Chrome()
browser.implicitly_wait(10)
browser.get('https://www.zhihu.com/explore')
input = browser.find_element_by_class_name('zu-top-add-question')
print(input)
显示等待
可以判断一些条件是否满足
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
browser = webdriver.Chrome()
browser.get('https://www.taobao.com')
wait = WebDriverWait(browser,10)
input = wait.until(EC.presence_of_element_located((By.ID,'q')))
button = wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR,'.btn-search')))
print(input,button)
<selenium.webdriver.remote.webelement.WebElement (session="eb554e111bd2e93c6f5c74b1ee29b705", element="0.663002834243013-1")> <selenium.webdriver.remote.webelement.WebElement (session="eb554e111bd2e93c6f5c74b1ee29b705", element="0.663002834243013-2")>
- title_is 标题是某内容
- title_contains 标题包含某内容
- presence_of_element_located 元素加载出,传入定位元组,如(By.ID,'p')
- visibility_of_element_located 元素可见,传入定位元组
- visibility_of 可见,传入元素对象
- presence_of_all_elements_located 所有元素加载出
- text_to_be_present_in_element 某个元素文本包含某文字
- text_to_be_present_in_element_value 某个元素值包含某文字
- frame_to_be_available_and_switch_to_it frame加载并切换
- invisibility_of _element_located 元素不可见
- element_to_be_clickable 元素可点击
- staleness_of 判断一个元素是否仍在DOM,可判断页面是否已经刷新
- element_to_be_selected 元素可选择,传元素对象
- element_located_to_be_selected 元素可选择,传入定位元组
- element_selection_state_to_be 传入元素对象以及状态,相等返回True,否则返回False
- element_located_selection_state_to_be 传入定位元组以及状态,相等返回True,否则返回False
- alert_is_present 是否出现Alert
前进后退
import time
from selenium import webdriver
browser = webdriver.Chrome()
browser.get('https://www.baidu.com/')
browser.get('https://www.taobao.com/')
browser.get('https://www.sina.com/')
browser.back()
time.sleep(1)
browser.forward()
browser.close()
Cookies
from selenium import webdriver
browser = webdriver.Chrome()
browser.get('https://www.zhihu.com/explore')
print(browser.get_cookies())
browser.add_cookie({'name':'name','domain':'www.zhihu.com','value':'germey'})
print(browser.get_cookies())
browser.delete_all_cookies()
print(browser.get_cookies())
选项卡管理
import time
打开两个窗口,并在第一个窗口跳转到第三个网页
from selenium import webdriver
browser = webdriver.Chrome()
browser.get('https://www.baidu.com')
browser.execute_script('window.open()')
print(browser.window_handles)
browser.switch_to_window(browser.window_handles[1])
browser.get('https://www.taobao.com')
time.sleep(1)
browser.switch_to_window(browser.window_handles[0])
browser.get('https://python.org')
异常处理
from selenium import webdriver
browser = webdriver.Chrome()
browser.get('https://www.baidu.com')
browser.find_element_by_id('hello')
Traceback (most recent call last):
File "basic3.py", line 5, in
browser.find_element_by_id('hello')
raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.NoSuchElementException: Message: no such element: Unable to locate element: {"method":"id","selector":"hello"}
(Session info: chrome=70.0.3538.77)
(Driver info: chromedriver=2.43.600233 (523efee95e3d68b8719b3a1c83051aa63aa6b10d),platform=Linux 4.15.0-39-generic x86_64)
from selenium import webdriver
from selenium.common.exceptions import TimeoutException,NoSuchElementException
browser = webdriver.Chrome()
try:
browser.get('https://www.baidu.com')
except TimeoutException:
print('Time Out')
try:
browser.find_element_by_id('hello')
except NoSuchElementException:
print('No Element')
finally:
browser.close()