1.下载第三方库及依赖项(可供离线安装)
    pip download -d 目标文件夹 库名称
    比如下载beautifulsoup4到 C:\workspace\python\thirdparty\thirdenv\dist-packages\beautifulsoup4-offline文件夹下：
    pip download -d C:\workspace\python\thirdparty\thirdenv\dist-packages\beautifulsoup4-offline beautifulsoup4

    pip3 download -d /home/guest/Downloads/lib/pillow pillow

    2.离线安装
    pip install —target=指定安装目录 —no-index —find-links=离线包所在目录 beautifulsoup4

    比如安装beautifulsoup4到C:\workspace\python\thirdparty\thirdenv\dist-packages\beautifulsoup4，从C:\workspace\python\thirdparty\thirdenv\dist-packages\beautifulsoup4-offline获取安装源
    pip install —target=C:\workspace\python\thirdparty\thirdenv\dist-packages\beautifulsoup4 —no-index —find-links=C:\workspace\python\thirdparty\thirdenv\dist-packages\beautifulsoup4-offline beautifulsoup4

    搜索顺序

    #test.py
    import sys

    for p ``in sys.path:
    print``(p)

    运行结果：
    C:\python ``/``/``pycharm环境中的Add content roots to PYTHONPATH
    C:\python ``/``/``脚本所在目录
    C:\Users\ihoney\AppData\Local\Programs\Python\Python35\python35.``zip /``/``打包,java扎包,避免大量小文件占空间
    C:\Users\ihoney\AppData\Local\Programs\Python\Python35\DLLs
    C:\Users\ihoney\AppData\Local\Programs\Python\Python35\lib
    C:\Users\ihoney\AppData\Local\Programs\Python\Python35
    C:\Users\ihoney\AppData\Local\Programs\Python\Python35\lib\site``-``packages ``/``/``第三方包安装路径
    C:\Users\ihoney\AppData\Local\Programs\Python\Python35\lib\site``-``packages\win32
    C:\Users\ihoney\AppData\Local\Programs\Python\Python35\lib\site``-``packages\win32\lib
    C:\Users\ihoney\AppData\Local\Programs\Python\Python35\lib\site``-``packages\Pythonwin

    多个python使用pip
    python -m pip list