1. 安装python
2. 安装Firefox http://www.firefox.com.cn/
3. sudo easy_install pip
4. sudo pip install -U selenium
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中间遇到的问题：
sudo pip install -U selenium
The directory '/Users/qiangma/Library/Caches/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
The directory '/Users/qiangma/Library/Caches/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
就是说目录不对，找了百度，解决方法：
1）sudo chown root -R qiangma /Users/qiangma/Library/Caches/pip/http
2）sudo chown root -R qiangma /Users/qiangma/Library/Caches/pip
然后再次执行sudo pip install -U selenium 就好了
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后面就要使用命令启动Firefox了
1.
python #进入python
2.
>>> from selenium import webdriver
>>> browser = webdriver.Firefox()
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再次遇到问题：
selenium.common.exceptions.WebDriverException: Message: 'geckodriver' executable needs to be in PATH.
解决方法：
下载geckodriver https://github.com/mozilla/geckodriver/releases
解压之后copy到目录/usr/local/bin/
（sudo cp ～/Downloads/geckodriver /usr/local/bin/）
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OK！