本想直接用pip install lxml 命令安装完事，但是由于安装过程中跟VS的一些东西冲突怎么都安装不上，搜索到以下方法，问题解决。
步骤：
1.下载跟python匹配的.whl 文件（lxml-3.6.0-cp35-cp35m-win_amd64.whl）下载地址 也可以下载附件，但未必适合你。
2.安装 python -m pip install lxml-3.6.0-cp35-cp35m-win_amd64.whl
可能出现的问题
lxml-3.6.0-cp35-cp35m-win_amd64.whl is not a supported wheel on this platform
版本不匹配，一定要对应版本
cp35 means CPython 3.5 you need lxml-3.6.0-cp35-cp35m-win_amd64.whl instead.
源自 *
Python 3.5 - how to install lxml in Windows 7 64 bits
1. go to this repository and download a version which matches your Python installation (the version number, and - vs -bit. I use Python 3.5. -bit, installed on Windows , so on that page, I chose lxml-3.6.-cp35-cp35m-win_amd64.whl. You say you use the -bit version, so use a version that matches that.
My download directory is d:\Downloads. Python must be in your PATH environment variable for the next step to work. Use a command like the following, changing "D:\Downloads" to the pathname to your download directory. Then, at a DOS prompt, type: 2. python -m pip install "D:\Downloads\lxml-3.6.0-cp35-cp35m-win_amd64.whl" lxml-3.6.-cp35-cp35m-win_amd64.whl