1、安装Homebrew
2、安装python3：brew install python3
•如果出现错误
Error: An unexpected error occurred during the `brew link` step
The formula built, but is not symlinked into /usr/local
Permission denied @ dir_s_mkdir - /usr/local/Frameworks
Error: Permission denied @ dir_s_mkdir - /usr/local/Frameworks
没有‘/usr/local/Frameworks’目录的话，创建创建一个
执行‘sudo chown username:admin /usr/local/Frameworks’
执行brew link python3
3、安装pip3：brew postinstall python3
如遇权限问题，可在所有命令前加sudo