Mac 上安装Python2.7和Python3

1 安装Xcode

xcode-select --install

2 安装Homebrew

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"


清华大学镜像
cd "$(brew --repo)"
git remote set-url origin https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/brew.git

cd "$(brew --repo)/Library/Taps/homebrew/homebrew-core"
git remote set-url origin https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/homebrew-core.git

brew update

3 安装Python

接下来要正式进入安装Python的步骤了！
首先，输入

python --version
打印出 Python 2.7.10 ，是mac自带的，不需要卸载

开始安装：
利用homebrew搜索Python

brew search python

会有如下结果：

app-engine-python  gst-python         python ✔           wxpython
boost-python       ipython            python-markdown    zpython
boost-python3      ipython@5          python-yq
boost-python@1.59  micropython        python@2 ✔

==> Casks
awips-python              kk7ds-python-runtime      mysql-connector-python

If you meant "python" specifically:
It was migrated from homebrew/cask to homebrew/core.

开始安装：

brew install python

brew install python3

查看安装的目录 /usr/local/Cellar/

4 设定路径$PATH (不和系统Python干扰)

执行 
1、echo $PATH
打印出
/usr/local/opt/gettext/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

打开 
2、sudo vim /etc/paths
系统会按以下顺序去索引
/usr/local/bin:
/usr/bin:
/bin:
/usr/sbin:
/sbin

5 安装完成，确认结果

which python
打印出  /usr/local/bin/python和/usr/local/bin/python3 说明安装正确

如果想使用系统的Python，就输入

/usr/bin/python

转载自 https://blog.csdn.net/hou_manager/article/details/79555809
个人怕忘记，所以简书上抄了一份过来，感谢分享。