google的驱动：chromedriver.exe
驱动版本与chrome版本对应的目录：
http://npm.taobao.org/mirrors/chromedriver/2.32/notes.txt
驱动各版本的下载地址：http://npm.taobao.org/mirrors/chromedriver
from selenium import webdriver
bs=webdriver.Chrome('C:\Program Files (x86)\Google\Chrome\Application\chromedriver')
chrome的首字母要大写，chromedriver要放到chrome.exe的目录下，调用时要给出chromedriver的全目录包括文件名‘chromedriver.exe’
Firefox的驱动：从前的版本好像不需要安装驱动，后来需要安装firefoxdriver.exe,
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Firefox Driver comes with Selenium/Webdriver itself. No need to launch an external server (like Chromedriver). It is all built-in. |
| note: as of selenium 3.0, FirefoxDriver has been replaced by GeckoDriver (which is external) |