下载官网 https://pip.pypa.io/en/latest/installing.html
官网截图如下：
Python 2.7.9 and later (on the python2 series), and Python 3.4 and later include pip by default [1], so you may have pip already.
To install pip, securely download get-pip.py. [2]
Then run the following (which may require administrator access):
python get-pip.py
安装selenium，联网状态的话，可以直接在C:\Python27\Scripts 下输入命令安装：
pip install -U selenium备注 ：若无联网，先把selenium-2.40.0.tar.gz解压到:C:\Python27\Lib\site-packages 目录下，打开命令提示符（开始---cmd 回车），使用cd命令进入C:\Python27\Lib\site-packages\ selenium-2.40.0目录下，输入python setup.py install回车，selenium安装完成
原文：http://www.cnblogs.com/yurenmeigui/p/4530750.html