mac下如何将python2.7改为python3

cd usr/local/Cellar/   //到此目录下
cd python/        //进入python目录下 查看已安装的python版本，如果有2.x 和 3.x说明安装成功

vi ~/.bash_profile  //编辑bash_profile

# Setting PATH for Python 3.7
# The orginal version is saved in .bash_profile.pysave
PATH="/Library/ works/Python. work/Versions/3.7/bin:${PATH}"
export PATH                                 //增加这几行内容（如果不是通过brew,而是通过官网下载安装，这里会默认已经添加了，就退出不用修改了）

sudo vi ~/.bashrc           //mac下需要管理员才能修改此文件  
alias python2='/System/Library/ works/Python. work/Versions/2.7/bin/python2.7'
alias python3='/Library/ works/Python. work/Versions/3.7/bin/python3.7'
alias python=python3
//添加以上三行 ， 如果不知道自己的python3安装路径，可以用 which python3 命令进行查看路径

source ~/.bash_profile
source ~/.bashrc