pip 安装 pycrypto 报错：Microsoft Visual C++ 14.0 is required. 的解决办法
环境：Win10 64位，Python版本 3.6
在CMD命令行用 pip.exe install pycrypto 安装PyCrypto模块时报错：
error: Microsoft Visual C++ 14.0 is required. Get it with "Microsoft Visual C++ Build Tools": http://landinghub.visualstudio.com/visual-cpp-build-tools
这是因为pycrypto模块编译需要依赖Visual C++ 14.0的编译工具，网上搜了一些方案，发现很多人遇到这个问题。（如果你是老实人，进那个网址，想安装
“Build Tools for Visual Studio 2017”的可以试试）自己也实践了下，踩过一些坑，总结的解决方案如下：
1. 安装Visual Studio 2015（C盘至少需要6G空间！没办法，不得不装）
下载地址在这里。
安装界面，只选择”Common Tools for VisualC++2015“。
等待漫长的安装过程安装完成。。。
安装完成后，再用pip安装，会报错如下：
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(26): error C2061: syntax error: identifier 'intmax_t'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(27): error C2061: syntax error: identifier 'rem'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(27): error C2059: syntax error: ';'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(28): error C2059: syntax error: '}'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(30): error C2061: syntax error: identifier 'imaxdiv_t'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(30): error C2059: syntax error: ';'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(40): error C2143: syntax error: missing '{' before '__cdecl'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(41): error C2146: syntax error: missing ')' before identifier '_Number'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(41): error C2061: syntax error: identifier '_Number'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(41): error C2059: syntax error: ';'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(42): error C2059: syntax error: ')'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(45): error C2143: syntax error: missing '{' before '__cdecl'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(46): error C2146: syntax error: missing ')' before identifier '_Numerator'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(46): error C2061: syntax error: identifier '_Numerator'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(46): error C2059: syntax error: ';'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(46): error C2059: syntax error: ','
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(48): error C2059: syntax error: ')'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(50): error C2143: syntax error: missing '{' before '__cdecl'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(56): error C2143: syntax error: missing '{' before '__cdecl'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(63): error C2143: syntax error: missing '{' before '__cdecl'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(69): error C2143: syntax error: missing '{' before '__cdecl'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(76): error C2143: syntax error: missing '{' before '__cdecl'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(82): error C2143: syntax error: missing '{' before '__cdecl'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(89): error C2143: syntax error: missing '{' before '__cdecl'
C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\inttypes.h(95): error C2143: syntax error: missing '{' before '__cdecl'
error: command 'D:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\BIN\\cl.exe' failed with exit status 2
这时按第2步操作。
2. 设置环境变量“VCINSTALLDIR”值为VC的安装路径，我的是“D:\Program Files (x86)\Microsoft Visual Studio 14.0\VC”（Visual Studio 2015安装界面默认VC是安装在C盘，可以修改安装在D盘！）。
3. 重新打开CMD，键入set CL=/FI"%VCINSTALLDIR%\\INCLUDE\\stdint.h" 。再用pip安装就可以成功。
注：在实践过程中，发现pip有可能报 UnicodeDecodeError: 'utf-8' codec can't decode byte... 错误，这时需要将CMD的终端编码用“CHCP 65001”命令改为“UTF-8”后再安装。
最后补张图：
