1.如果有别的不需要的版本可以卸载，例如卸载3.6，安装3.7
1.1 删除Python 3.6 framework
sudo rm -rf /Library/Frameworks/Python.framework/Versions/3.6
1.2 删除Python 3.6 应用目录
sudo rm -rf "/Applications/Python 3.6"
1.3 删除/usr/local/bin 目录下指向的Python3.6的连接
cd /usr/local/bin/
ls -l /usr/local/bin | grep '../Library/Frameworks/Python.framework/Versions/3.6' | awk '{print $9}' | tr -d @ | xargs rm
2.安装python3.7
2.1 在官网上下载pkg，点击安装
2.2 检查.bash_profile
open -e .bash_profile // 打开
内容为：
# Setting PATH for Python 3.7
# The original version is saved in .bash_profile.pysave
PATH="/Library/Frameworks/Python.framework/Versions/3.7/bin:${PATH}"
export PATH
注意：如果之前里面有3.6的需要删掉，然后
source .bash_profile