PYTHON 爬虫笔记七:Selenium库基础用法

时间：2023-03-08 17:14:41

知识点一：Selenium库详解及其基本使用

  • 什么是Selenium

　　　　selenium 是一套完整的web应用程序测试系统，包含了测试的录制（selenium IDE）,编写及运行（Selenium Remote Control）和测试的并行处理（Selenium Grid）。

　　　　　　selenium的核心Selenium Core基于JsUnit，完全由JavaScript编写，因此可以用于任何支持JavaScript的浏览器上。

　　　　　　selenium可以模拟真实浏览器，自动化测试工具，支持多种浏览器，爬虫中主要用来解决JavaScript渲染问题。

  • 基本使用

　用python写爬虫的时候，主要用的是selenium的Webdriver，我们可以通过下面的方式先看看Selenium.Webdriver支持哪些浏览器

  1. 基本用法：

    #打开google浏览器，再打开百度，输入Python然后按回车
    
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

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
    
browser = webdriver.Chrome(chromedriver)
    
try:
    
    browser.get('https://www.baidu.com')
    
    input = browser.find_element_by_id('kw')  # 找到id为kw的元素
    
    input.send_keys('Python')  # 敲入Python
    
    input.send_keys(Keys.ENTER)  # 敲入回车
    
    wait = WebDriverWait(browser, 10)
    
    wait.until(EC.presence_of_element_located((By.ID, 'content_left')))  # 等待某个元素加载出来
    
    print(browser.current_url)
    
    print(browser.get_cookies())
    
    print(browser.page_source)  # 网页源代码
    
finally:
    
    browser.close()
    https://www.baidu.com/s?ie=utf-8&f=8&rsv_bp=0&rsv_idx=1&tn=baidu&wd=Python&rsv_pq=aa95af1b0000f45e&rsv_t=53e2qpjWA%2FivTq6GgdT4FAhWM%2FWfkPZhHYkLoaS7MVPQUZCHF%2FkLQV2%2Brnc&rqlang=cn&rsv_enter=1&rsv_sug3=6&rsv_sug2=0&inputT=111&rsv_sug4=112
    
[{'domain': '.baidu.com', 'httpOnly': False, 'name': 'H_PS_PSSID', 'path': '/', 'secure': False, 'value': '1464_21121_26922_22159'}, {'domain': '.baidu.com', 'expiry': 3681286522.89887, 'httpOnly': False, 'name': 'BAIDUID', 'path': '/', 'secure': False, 'value': '410FC9CBBC1B798C0BEF149D5C0BD4E4:FG=1'}, {'domain': '.baidu.com', 'expiry': 3681286522.899111, 'httpOnly': False, 'name': 'BIDUPSID', 'path': '/', 'secure': False, 'value': '410FC9CBBC1B798C0BEF149D5C0BD4E4'}, {'domain': '.baidu.com', 'expiry': 3681286522.899241, 'httpOnly': False, 'name': 'PSTM', 'path': '/', 'secure': False, 'value': ''}, {'domain': '.baidu.com', 'httpOnly': False, 'name': 'PSINO', 'path': '/', 'secure': False, 'value': ''}, {'domain': 'www.baidu.com', 'expiry': 2479882880.172246, 'httpOnly': False, 'name': 'delPer', 'path': '/', 'secure': False, 'value': ''}, {'domain': 'www.baidu.com', 'httpOnly': False, 'name': 'BD_HOME', 'path': '/', 'secure': False, 'value': ''}, {'domain': 'www.baidu.com', 'expiry': 1534666877, 'httpOnly': False, 'name': 'BD_UPN', 'path': '/', 'secure': False, 'value': ''}, {'domain': 'www.baidu.com', 'httpOnly': False, 'name': 'BD_CK_SAM', 'path': '/', 'secure': False, 'value': ''}, {'domain': 'www.baidu.com', 'expiry': 1533805472, 'httpOnly': False, 'name': 'H_PS_645EC', 'path': '/', 'secure': False, 'value': 'c9083HSTzGdEsBVBx%2FDjhaEep8Lu5MHd8KusVOaaun2nj5W%2Bjur8%2BSHut%2BM'}]
    
<!DOCTYPE html><!--STATUS OK--><html xmlns="http://www.w3.org/1999/xhtml"><head><script charset="utf-8" async="" src="https://ss0.bdstatic.com/-0U0bnSm1A5BphGlnYG/tam-ogel/5d4e9b24-dcc5-483a-b6da-be1e9e621891.js"></script>

    获得的结果

  2. 声明浏览器对象（上面我们知道了selenium支持很多的浏览器，但是如果想要声明并调用浏览器则需要：）

    from selenium import webdriver

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

  3. 访问页面

    from selenium import webdriver

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
    
browser = webdriver.Chrome(chromedriver)
    
browser.get('https://www.taobao.com')
    
print(browser.page_source)
    
browser.close()
    <!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml" lang="zh-CN" class="ks-webkit537 ks-webkit ks-chrome68 ks-chrome"><head><script>/*! 2018-08-07 14:58:00 v8.5.7 */
    
!function(e){function i(n){if(o[n])return o[n].exports;var r=o[n]={exports:{},id:n,loaded:!1};return e[n].call(r.exports,r,r.exports,i),r.loaded=!0,r.exports}var o={};return i.m=e,i.c=o,i.p="",i(0)}([function(e,i){"use strict";var o=window,n=document;!function(){var e=2,r="ali_analytics";if(o[r]&amp;&amp;o[r].ua&amp;&amp;e&lt;=o[r].ua.version)return void(i.info=o[r].ua);var t,a,d,s,c,u,h,l,m,b,f,v,p,w,g,x,z,O=o.navigator,k=O.appVersion,T=O&amp;&amp;O.userAgent||"",y=function(e){var i=0;return parseFloat(e.replace(/\./g,function(){return 0===i++?".":""}))},_=function(e,i){var o,n;i[o="trident"]=.1,(n=e.match(/Trident\/([\d.]*)/))&amp;&amp;n[1]&amp;&amp;(i[o]=y(n[1])),i.core=o},N=function(e){var i,o;return(i=e.match(/MSIE ([^;]*)|Trident.*; rv(?:\s|:)?([0-9.]+)/))&amp;&amp;(o=i[1]||i[2])?y(o):0},P=function(e){return e||"other"},M=function(e){function i(){for(var i=[["Windows NT 5.1","winXP"],["Windows NT 6.1","win7"],["Windows NT 6.0","winVista"],["Windows NT 6.2","win8"],["Windows NT 10.0","win10"],["iPad","ios"],["iPhone;","ios"],["iPod","ios"],["Macintosh","mac"],["Android","android"],["Ubuntu","ubuntu"],["Linux","linux"],["Windows NT 5.2","win2003"],["Windows NT 5.0","win2000"],["Windows","winOther"],["rhino","rhino"]],o=0,n=i.length;o&lt;n;++o)if(e.indexOf(i[o][0])!==-1)return i[o][1];return"other"}function r(e,i,n,r){var t,a=o.navigator.mimeTypes;try{for(t in a)if(a.hasOwnProperty(t)&amp;&amp;a[t][e]==i){if(void 0!==n&amp;&amp;r.test(a[t][n]))return!0;if(void 0===n)return!0}return!1}catch(e){return!1}}var t,a,d,s,c,u,h,l="",m=l,b=l,f=[6,9],v="{{version}}",p="&lt;!--[if IE "+v+"]&gt;&lt;s&gt;&lt;/s&gt;&lt;![endif]--&gt;",w=n&amp;&amp;n.createElement("div"),g=[],x={webkit:void 0,edge:void 0,trident:void 0,gecko:void 0,presto:void 0,chrome:void 0,safari:void 0,firefox:void 0,ie:void 0,ieMode:void 0,opera:void 0,mobile:void 0,core:void 0,shell:void 0,phantomjs:void 0,os:void 0,ipad:void 0,iphone:void 0,ipod:void 0,ios:void 0,android:void 0,nodejs:void 0,extraName:void 0,extraVersion:void 0};if(w&amp;&amp;w.getElementsByTagName&amp;&amp;(w.innerHTML=p.replace(v,""),g=w.getElementsByTagName("s")),g.length&gt;0){for(_(e,x),s=f[0],c=f[1];s&lt;=c;s++)if(w.innerHTML=p.replace(v,s),g.length&gt;0){x[b="ie"]=s;break}!x.ie&amp;&amp;(d=N(e))&amp;&amp;(x[b="ie"]=d)}else((a=e.match(/AppleWebKit\/*\s*([\d.]*)/i))||(a=e.match(/Safari\/([\d.]*)/)))&amp;&amp;a[1]?(x[m="webkit"]=y(a[1]),(a=e.match(/OPR\/(\d+\.\d+)/))&amp;&amp;a[1]?x[b="opera"]=y(a[1]):(a=e.match(/Chrome\/([\d.]*)/))&amp;&amp;a[1]?x[b="chrome"]=y(a[1]):(a=e.match(/\/([\d.]*) Safari/))&amp;&amp;a[1]?x[b="safari"]=y(a[1]):x.safari=x.webkit,(a=e.match(/Edge\/([\d.]*)/))&amp;&amp;a[1]&amp;&amp;(m=b="edge",x[m]=y(a[1])),/ Mobile\//.test(e)&amp;&amp;e.match(/iPad|iPod|iPhone/)?(x.mobile="apple",a=e.match(/OS ([^\s]*)/),a&amp;&amp;a[1]&amp;&amp;(x.ios=y(a[1].replace("_","."))),t="ios"。。。。。。。。。。。

    获得的结果

  4. 查找元素

    1. 单个元素

      #element
      
from selenium import webdriver

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
      
browser = webdriver.Chrome(chromedriver)
      
browser.get('https://www.taobao.com')
      
input_first = browser.find_element_by_id('q')  #　寻找 id='q'的元素
      
input_second = browser.find_element_by_css_selector('#q')  # 通过css选择器选择
      
input_third = browser.find_element_by_xpath('//*[@id="q"]')  # 同上
      
print(input_first, input_second, input_third)
      
browser.close()
      　　  #这里我们通过三种不同的方式去获取响应的元素，第一种是通过id的方式，第二个中是CSS选择器，第三种是xpath选择器，结果都是相同的。
      <selenium.webdriver.remote.webelement.WebElement (session="49795084aea9c702e52e3464a2e602bf", element="0.06918141330676386-1")> <selenium.webdriver.remote.webelement.WebElement (session="49795084aea9c702e52e3464a2e602bf", element="0.06918141330676386-1")> <selenium.webdriver.remote.webelement.WebElement (session="49795084aea9c702e52e3464a2e602bf", element="0.06918141330676386-1")>

      获得的结果

      另一种方式：
      from selenium import webdriver
      
from selenium.webdriver.common.by import By

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
      
browser = webdriver.Chrome(chromedriver)
      
browser.get('https://www.taobao.com')
      
input_first = browser.find_element(By.ID, 'q')
      
print(input_first)
      
browser.close()

      另一种方式

      <selenium.webdriver.remote.webelement.WebElement (session="2706eb775a80e5eb5af01293caaf84e1", element="0.30861434960698597-1")>

      --->获得的结果

      查找单个元素的方法
      * 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

    2. 查找多个元素

      #elements
      
from selenium import webdriver

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
      
browser = webdriver.Chrome(chromedriver)
      
browser.get('https://www.taobao.com')
      
lis = browser.find_elements_by_css_selector('.service-bd li')
      
print(lis)
      
browser.close()
      [<selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-1")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-2")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-3")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-4")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-5")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-6")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-7")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-8")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-9")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-10")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-11")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-12")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-13")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-14")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-15")>, <selenium.webdriver.remote.webelement.WebElement (session="1fd716bf2cf93a91caa11907d2ad67c7", element="0.7320173413952247-16")>]

      获得的结果

      另一种方式：
      from selenium import webdriver
      
from selenium.webdriver.common.by import By

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
      
browser = webdriver.Chrome(chromedriver)
      
browser.get('https://www.taobao.com')
      
lis = browser.find_elements(By.CSS_SELECTOR, '.service-bd li')
      
print(lis)
      
browser.close()

      另一种方式

      [<selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-1")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-2")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-3")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-4")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-5")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-6")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-7")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-8")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-9")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-10")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-11")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-12")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-13")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-14")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-15")>, <selenium.webdriver.remote.webelement.WebElement (session="f8d8a0f755dde2eecb7de8970c44d9f5", element="0.5842041920354057-16")>]

      --->获得的结果

      一些其他的方式：

      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

  5. 元素交互操作

    先获取元素。
    对获取的元素调用交互方法

    from selenium import webdriver
    
import time

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
    
browser = webdriver.Chrome(chromedriver)
    
browser.get('https://www.taobao.com')
    
input = browser.find_element_by_id('q')  # 找到搜索框
    
input.send_keys('iPhone')  # 输入 iPhone
    
time.sleep(1)  # 等待一秒
    
input.clear()  # 清空文本框
    
input.send_keys('iPad')  # 输入ipad
    
button = browser.find_element(By.CLASS_NAME,'btn-search')  # 找到搜索按钮
    
button.click()  # 点击
    
browser.close()

    更多操作: http://selenium-python.readthedocs.io/api.html#module-selenium.webdriver.remote.webelement

  6. 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

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
    
browser = webdriver.Chrome(chromedriver) # 声明浏览器对象
    
url = 'http://www.runoob.com/try/try.php?filename=jqueryui-api-droppable'
    
browser.get(url)
    
browser.switch_to.frame('iframeResult')  #切换到‘iframeResult’框架
    
source = browser.find_element_by_css_selector('#draggable')  # 选择元素
    
target = browser.find_element_by_css_selector('#droppable')  # 选择元素
    
actions = ActionChains(browser)  # 声明一个动作链对象
    
actions.drag_and_drop(source, target)  # 拖拽方法
    
actions.perform()  # 执行动作

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

  7. 执行JavaScript（执行一些交互动作时，可能一些动作没有提供API。）

    #把网页拉到最下面，并提示
    
from selenium import webdriver

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
    
browser = webdriver.Chrome(chromedriver) # 声明浏览器对象

browser.get('https://www.zhihu.com/explore')
    
browser.execute_script('window.scrollTo(0, document.body.scrollHeight)')
    
browser.execute_script('alert("To Bottom")')

  8. 获取元素信息

    1. 获取属性：*.get_attribute(“class”) *

      from selenium import webdriver
      
from selenium.webdriver import ActionChains

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
      
browser = webdriver.Chrome(chromedriver) # 声明浏览器对象
      
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'))
      
browser.close()
      <selenium.webdriver.remote.webelement.WebElement (session="d5564ba9ec58a9a53015648f61a56bd7", element="0.46068206240103504-1")>
      
zu-top-link-logo

      获得的结果

    2. 获取文本值：*text*

      from selenium import webdriver

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
      
browser = webdriver.Chrome(chromedriver) # 声明浏览器对象
      
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

    3. 获取ID、位置、标签名、大小

      from selenium import webdriver

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
      
browser = webdriver.Chrome(chromedriver) # 声明浏览器对象
      
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)
      0.0866191825002236-1
      
{'x': 759, 'y': 7}
      
button
      
{'height': 32, 'width': 66}

      获得的结果

    4. Frame

      在很多网页中都是有Frame标签，所以我们爬取数据的时候就涉及到切入到frame中以及切出来的问题，通过下面的例子演示
      
这里常用的是switch_to.from()和switch_to.parent_frame()
      
父级的frame要查找子级的frame必须要切换到子frame，否则不能查找。
      
同理子frame也不能查找父frame的元素。
      import time
      
from selenium import webdriver
      
from selenium.common.exceptions import NoSuchElementException

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
      
browser = webdriver.Chrome(chromedriver)
      
url = 'http://www.runoob.com/try/try.php?filename=jqueryui-api-droppable'  # 声明网址
      
browser.get(url)  # get传入网址
      
browser.switch_to.frame('iframeResult')  # 切换到子frame
      
source = browser.find_element_by_css_selector('#draggable')  # 查找子frame中的元素
      
print(source)
      
try:
      
    logo = browser.find_element_by_class_name('logo')
      
except NoSuchElementException:
      
    print('NO LOGO')
      
browser.switch_to.parent_frame()  # 切换到父frame
      
logo = browser.find_element_by_class_name('logo')
      
print(logo)
      
print(logo.text)
      <selenium.webdriver.remote.webelement.WebElement (session="7d3651ff77a4266e974a48387a562fe1", element="0.7541880746473664-1")>
      
NO LOGO
      
<selenium.webdriver.remote.webelement.WebElement (session="7d3651ff77a4266e974a48387a562fe1", element="0.04296955550550363-2")>
      
RUNOOB.COM

      获得的结果

  9. 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

    1. 隐式等待　　

      到了一定的时间发现元素还没有加载，则继续等待我们指定的时间，如果超过了我们指定的时间还没有加载就会抛出异常，如果没有需要等待的时候就已经加载完毕就会立即执行
      from selenium import webdriver

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
      
browser = webdriver.Chrome(chromedriver)
      
browser.implicitly_wait(10)  # 传入隐式等待的时间
      
browser.get('https://www.zhihu.com/explore')
      
input = browser.find_element_by_class_name('zu-top-add-question')
      
print(input)
      <selenium.webdriver.remote.webelement.WebElement (session="7c232ca91150077a6d9ded5a653ebf6d", element="0.019205089543862464-1")>

      获得的结果

    2. 显式等待：* .WebDriverWait(对象，最长等待时间)*

      指定一个等待条件，并且指定一个最长等待时间，会在这个时间内进行判断是否满足等待条件，如果成立就会立即返回，如果不成立，就会一直等待，直到等待你指定的最长等待时间，
      如果还是不满足，就会抛出异常，如果满足了就会正常返回
      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

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
      
browser = webdriver.Chrome(chromedriver)
      
browser.get('https://www.taobao.com/')
      
wait = WebDriverWait(browser, 10)  # 声明一个等待对象
      
# 判断元素是否加载
      
input = wait.until(EC.presence_of_element_located((By.ID, 'q')))  # 传入等待条件
      
# # 判断是否可点击的，一般用来判断是否为按钮
      
button = wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR, '.btn-search')))
      
print(input, button)
      <selenium.webdriver.remote.webelement.WebElement (session="ac4d3c5db3d4f3aae7b828ad648e87df", element="0.49320541507860316-1")> <selenium.webdriver.remote.webelement.WebElement (session="ac4d3c5db3d4f3aae7b828ad648e87df", element="0.49320541507860316-2")>

      获得的结果

      上述的例子中的条件：
      EC.presence_of_element_located()是确认元素是否已经出现了
      EC.element_to_be_clickable()是确认元素是否是可点击的

      常用的判断条件：
      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

      更多操作参考：http://selenium-python.readthedocs.io/api.html#module-selenium.webdriver.support.expected_conditions

  10. 前进后退：*back()；forward()*

    #打开谷歌浏览器，然后打开白队首页，在打开淘宝，知乎首页，返回淘宝页面等待一秒在回到知乎界面
    
import time
    
from selenium import webdriver

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
    
browser = webdriver.Chrome(chromedriver)
    
browser.get('https://www.baidu.com/')
    
browser.get('https://www.taobao.com/')
    
browser.get('https://www.zhihu.com/')
    
browser.back()
    
time.sleep(1)
    
browser.forward()
    
browser.close()

  11. Cookies：*get_cookies()；delete_all_cookes()；add_cookie()*

    from selenium import webdriver

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
    
browser = webdriver.Chrome(chromedriver)
    
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())
    [{'domain': '.zhihu.com', 'httpOnly': False, 'name': 'l_n_c', 'path': '/', 'secure': False, 'value': ''}, {'domain': 'www.zhihu.com', 'expiry': 1533802053.671843, 'httpOnly': False, 'name': 'tgw_l7_route', 'path': '/', 'secure': False, 'value': '156dfd931a77f9586c0da07030f2df36'}, {'domain': '.zhihu.com', 'expiry': 1533802958, 'httpOnly': False, 'name': '__utmb', 'path': '/', 'secure': False, 'value': '51854390.0.10.1533801158'}, {'domain': '.zhihu.com', 'expiry': 1628409153.672149, 'httpOnly': False, 'name': 'q_c1', 'path': '/', 'secure': False, 'value': '5fdfbadd6fc347398cc287ebb19a383c|1533801155000|1533801155000'}, {'domain': 'www.zhihu.com', 'httpOnly': False, 'name': '_xsrf', 'path': '/', 'secure': False, 'value': 'e58e3a1c1f41931b44a67c2b426c2f1e'}, {'domain': '.zhihu.com', 'expiry': 1536393153.672288, 'httpOnly': False, 'name': 'r_cap_id', 'path': '/', 'secure': False, 'value': '"MjI4MWJhNjU3YTRiNGFkMmE0OTkxNjk5MDMxZjc4NTU=|1533801155|61d044a51d2c7f0c8a99b9efcdec2f929a626003"'}, {'domain': '.zhihu.com', 'expiry': 1536393153.672375, 'httpOnly': False, 'name': 'cap_id', 'path': '/', 'secure': False, 'value': '"OTQ3Mjc1NmI0ZWEyNDFiOTkwYjAxYmY5NmU5Y2YyZGY=|1533801155|e2f66995a8136044730315e95ab3230932d3e85a"'}, {'domain': '.zhihu.com', 'expiry': 1536393153.672453, 'httpOnly': False, 'name': 'l_cap_id', 'path': '/', 'secure': False, 'value': '"NzRiMmNiMGQ2ZjYwNGIwM2I2Nzg0OTExNGUxZTJmZTA=|1533801155|9ad2a89322a8cfaf04770121c359a1de82636336"'}, {'domain': '.zhihu.com', 'httpOnly': False, 'name': 'n_c', 'path': '/', 'secure': False, 'value': ''}, {'domain': '.zhihu.com', 'expiry': 1628409157.390474, 'httpOnly': False, 'name': 'd_c0', 'path': '/', 'secure': False, 'value': '"ALDleMF-Bw6PTmu-31M1eULrY7jjkGvu9tA=|1533801158"'}, {'domain': '.zhihu.com', 'expiry': 1596873157, 'httpOnly': False, 'name': '_zap', 'path': '/', 'secure': False, 'value': '084e48e3-598e-4d8a-85b4-4def087fc321'}, {'domain': '.zhihu.com', 'expiry': 1596873158, 'httpOnly': False, 'name': '__utma', 'path': '/', 'secure': False, 'value': '51854390.543124770.1533801158.1533801158.1533801158.1'}, {'domain': '.zhihu.com', 'httpOnly': False, 'name': '__utmc', 'path': '/', 'secure': False, 'value': ''}, {'domain': '.zhihu.com', 'expiry': 1549569158, 'httpOnly': False, 'name': '__utmz', 'path': '/', 'secure': False, 'value': '51854390.1533801158.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)'}, {'domain': '.zhihu.com', 'expiry': 1596873158, 'httpOnly': False, 'name': '__utmv', 'path': '/', 'secure': False, 'value': '51854390.000--|3=entry_date=20180809=1'}]
    
[{'domain': '.zhihu.com', 'httpOnly': False, 'name': 'l_n_c', 'path': '/', 'secure': False, 'value': ''}, {'domain': 'www.zhihu.com', 'expiry': 1533802053.671843, 'httpOnly': False, 'name': 'tgw_l7_route', 'path': '/', 'secure': False, 'value': '156dfd931a77f9586c0da07030f2df36'}, {'domain': '.zhihu.com', 'expiry': 1533802958, 'httpOnly': False, 'name': '__utmb', 'path': '/', 'secure': False, 'value': '51854390.0.10.1533801158'}, {'domain': '.zhihu.com', 'expiry': 1628409153.672149, 'httpOnly': False, 'name': 'q_c1', 'path': '/', 'secure': False, 'value': '5fdfbadd6fc347398cc287ebb19a383c|1533801155000|1533801155000'}, {'domain': 'www.zhihu.com', 'httpOnly': False, 'name': '_xsrf', 'path': '/', 'secure': False, 'value': 'e58e3a1c1f41931b44a67c2b426c2f1e'}, {'domain': '.zhihu.com', 'expiry': 1536393153.672288, 'httpOnly': False, 'name': 'r_cap_id', 'path': '/', 'secure': False, 'value': '"MjI4MWJhNjU3YTRiNGFkMmE0OTkxNjk5MDMxZjc4NTU=|1533801155|61d044a51d2c7f0c8a99b9efcdec2f929a626003"'}, {'domain': '.zhihu.com', 'expiry': 1536393153.672375, 'httpOnly': False, 'name': 'cap_id', 'path': '/', 'secure': False, 'value': '"OTQ3Mjc1NmI0ZWEyNDFiOTkwYjAxYmY5NmU5Y2YyZGY=|1533801155|e2f66995a8136044730315e95ab3230932d3e85a"'}, {'domain': '.zhihu.com', 'expiry': 1536393153.672453, 'httpOnly': False, 'name': 'l_cap_id', 'path': '/', 'secure': False, 'value': '"NzRiMmNiMGQ2ZjYwNGIwM2I2Nzg0OTExNGUxZTJmZTA=|1533801155|9ad2a89322a8cfaf04770121c359a1de82636336"'}, {'domain': '.zhihu.com', 'httpOnly': False, 'name': 'n_c', 'path': '/', 'secure': False, 'value': ''}, {'domain': '.zhihu.com', 'expiry': 1628409157.390474, 'httpOnly': False, 'name': 'd_c0', 'path': '/', 'secure': False, 'value': '"ALDleMF-Bw6PTmu-31M1eULrY7jjkGvu9tA=|1533801158"'}, {'domain': '.zhihu.com', 'expiry': 1596873157, 'httpOnly': False, 'name': '_zap', 'path': '/', 'secure': False, 'value': '084e48e3-598e-4d8a-85b4-4def087fc321'}, {'domain': '.zhihu.com', 'expiry': 1596873158, 'httpOnly': False, 'name': '__utma', 'path': '/', 'secure': False, 'value': '51854390.543124770.1533801158.1533801158.1533801158.1'}, {'domain': '.zhihu.com', 'httpOnly': False, 'name': '__utmc', 'path': '/', 'secure': False, 'value': ''}, {'domain': '.zhihu.com', 'expiry': 1549569158, 'httpOnly': False, 'name': '__utmz', 'path': '/', 'secure': False, 'value': '51854390.1533801158.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)'}, {'domain': '.zhihu.com', 'expiry': 1596873158, 'httpOnly': False, 'name': '__utmv', 'path': '/', 'secure': False, 'value': '51854390.000--|3=entry_date=20180809=1'}, {'domain': 'www.zhihu.com', 'expiry': 2164521158, 'httpOnly': False, 'name': 'name', 'path': '/', 'secure': True, 'value': 'germey'}]
    
[]

    获得的结果

  12. 选项卡管理

    通过执行js命令实现新开选项卡window.open()
    
不同的选项卡是存在列表里browser.window_handles
    
通过browser.window_handles[0]就可以操作第一个选项卡
    import time
    
from selenium import webdriver

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
    
browser = webdriver.Chrome(chromedriver)
    
browser.get('https://www.baidu.com')
    
browser.execute_script('window.open()')  # 通过执行一个js语句来新建选项卡
    
print(browser.window_handles)  # 返回所有的选项卡的引用
    
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')
    ['CDwindow-B1E2119962846BA7AED735D128600D3E', 'CDwindow-B231BF356905D63DE59F86F644F77A8F']

    获得的结果

  13. 异常处理

    这里的异常比较复杂，官网的参考地址：
    http://selenium-python.readthedocs.io/api.html#module-selenium.common.exceptions
    这里只进行简单的演示，查找一个不存在的元素

    1. 实例，会报错

      from selenium import webdriver

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
      
browser = webdriver.Chrome(chromedriver)
      
browser.get('https://www.baidu.com')
      
browser.find_element_by_id('hello')
      NoSuchElementException                    Traceback (most recent call last)
      
<ipython-input-15-b8bcc6bfca0b> in <module>()
      
      4 browser = webdriver.Chrome(chromedriver)
      
      5 browser.get('https://www.baidu.com')
      
----> 6 browser.find_element_by_id('hello')

D:\Anaconda3\lib\site-packages\selenium\webdriver\remote\webdriver.py in find_element_by_id(self, id_)
      
    357             element = driver.find_element_by_id('foo')
      
    358         """
      
--> 359         return self.find_element(by=By.ID, value=id_)
      
    360
      
    361     def find_elements_by_id(self, id_):

D:\Anaconda3\lib\site-packages\selenium\webdriver\remote\webdriver.py in find_element(self, by, value)
      
    964         return self.execute(Command.FIND_ELEMENT, {
      
    965             'using': by,
      
--> 966             'value': value})['value']
      
    967
      
    968     def find_elements(self, by=By.ID, value=None):

D:\Anaconda3\lib\site-packages\selenium\webdriver\remote\webdriver.py in execute(self, driver_command, params)
      
    318         response = self.command_executor.execute(driver_command, params)
      
    319         if response:
      
--> 320             self.error_handler.check_response(response)
      
    321             response['value'] = self._unwrap_value(
      
    322                 response.get('value', None))

D:\Anaconda3\lib\site-packages\selenium\webdriver\remote\errorhandler.py in check_response(self, response)
      
    240                 alert_text = value['alert'].get('text')
      
    241             raise exception_class(message, screen, stacktrace, alert_text)
      
--> 242         raise exception_class(message, screen, stacktrace)
      
    243
      
    244     def _value_or_default(self, obj, key, default):

NoSuchElementException: Message: no such element: Unable to locate element: {"method":"id","selector":"hello"}
      
  (Session info: chrome=68.0.3440.75)
      
  (Driver info: chromedriver=2.41.578737 (49da6702b16031c40d63e5618de03a32ff6c197e),platform=Windows NT 10.0.17134 x86_64)

      获得的结果

    2. 抛出异常 
      from selenium import webdriver
      
from selenium.common.exceptions import TimeoutException, NoSuchElementException

chromedriver = "C:/Program Files (x86)/Google/Chrome/Application/chromedriver"
      
browser = webdriver.Chrome(chromedriver)
      
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()
      No Element

      获得的结果　　　

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