Selenium

Selenium 崔老师爬虫系列课程学习笔记

自动化测试工具,支持多种浏览器。
爬虫中主要用来解决JavaSript的渲染问题
当通过requests和urllib库无法获得网页内容,这个时候可以用Selenium库来模拟浏览器

安装

pip install selenium

基本使用

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('http://www.baidu.com')# 传入网址
    input = browser.find_element_by_id('kw')#找出id为kw的元素
    input.send_keys('Python')# 像元素中发送python字符串
    input.send_keys(Keys.ENTER)# 传入Enter键
    wait = WebDriverWait(browser,10)
    wait.until(EC.presence_of_element_located((By.ID,'content_left')))
    print(browser.current_url)#打出此时的url
    print(browser.get_cookies)#打印出cookies
    print(browser.page_source)#打印出源代码
finally:
    browser.close()

声明浏览器对象

        from selenium import webdriver

browserser = webdriver.Chrome()
browser = webdriver.Firefox()
browser = webdriver.Edge()
browser = webdriver.PhantomJS()

访问页面

from selenium import webdriver
browser = webdriver.Chrome()
browser.get('https://www.taobao.com')
print(browser.page_source())

查找元素

单个元素

from selenium import webdriver

browser = webdriver.Chrome()
browser.get('http://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)

find_element_by_name

find_element_by_xpath

find_element_by_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_first = browser.find_element(By.ID,'q')
print(input_first)
#browser.close()

多个元素

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)

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)

元素交互操作

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)#请求一个url
browser.switch_to.frame('iframeResult')#切换到一个frame
source = browser.find_element_by_css_selector('#draggable')#找到要拖拽对象
target = browser.find_element_by_css_selector('#droppable')#找到目标位置
actions = ActionChains(browser)
actions.drag_and_drop(source,target)
actions.perform()

更多动作:http://selenium-python.readthedocs.io/api.html#module-selenium.webdriver.common.action_chains

执行JavaScript

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'))

获取文本值

from selenium import webdriver

browser = webdriver.Chrome()
url = ('https://www.zhihu.com/explore')
browser.get(url)
input = browser.find_element_by_class_name('zu-top-add-question')
print(input.text)
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)
input = browser.find_element_by_class_name('zu-top-add-question')
print(input.id)
print(input.location)
print(input.tag_name)
print(input.size)

Frame

from selenium import webdriver

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_elememt_by_class_name('logo')
except Exception:
    print('NoLogo')

browser.switch_to.parent_frame()

logo = browser.find_element_by_class_name('logo')
print(logo)
print(logo.text)    

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,默认的时间是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.text)
提问

显式等待

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)

详细内容:http://selenium-python.readthedocs.io/api.html#module-selenium.webdriver.support.expected_conditions

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.python.org/')
browser.back()
time.sleep(9)
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

from selenium import webdriver
browser= webdriver.Chrome()
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(5)
browser.switch_to_window(browser.window_handles[0])
browser.get('https://python.org')

异常处理

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()

详细文档:http://selenium-python.readthedocs.io/api.html#module-selenium.common.exceptions

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