Python安装：Mac 使用brew 安装Python2 和 Python3

安装python

## python2
brew install python  

## python3
brew install python3

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

解决

手动创建目录

$ sudo mkdir /usr/local/Frameworks
$ sudo chown $(whoami):admin /usr/local/Frameworks

查看版本

$ which python
/usr/bin/python

$ python --version
Python 2.7.16

设置环境变量

## 打开配置文件，如果没有就在~目录下面创建一个
$ open ~/.bash.profile

设置python环境变量路径

# Setting PATH for Python 2.7 系统自带python2
PATH="/System/Library/Frameworks/Python.framework/Versions/2.7/bin:${PATH}"  -
export PATH

# Setting PATH for Python 3.7.5 brew安装的python3
PATH="/usr/local/Cellar/python/3.7.5/bin:${PATH}"

## 设置别名 注意目录看下是否正确
alias python2='/System/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7'
alias python3='/usr/local/Cellar/python/3.7.5/bin/python3'
# alias python=python3

生效配置文件

source ~/.bash.profile 

验证

## python 和 python2 都指向python2
$ python --version
$ python2 --version
$ python3 --version