Mac默认是集成Python 环境的，一般是2版本。你可以在终端输入命令看一下：
zhangyudeiMac:~ zhangyu$ python
Python 2.7.10 (default, Jul 15 2017, 17:16:57)
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.31)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>
我们想要安装下python3有两种方法安装：
一、第一种直接去官网下载安装： https://www.python.org/downloads/mac-osx/，有些人感觉这样装有点不能装逼。重点说下brew安装吧，
二、homebrew 安装，如果你是使用Mac的程序员，一定知道这个吧，本人很喜欢。如果不知道点这里傻瓜式教学安装。
Homebrew安装Python3详细步骤指令：
1、执行 brew search python
==> Searching local taps...
app-engine-python gst-python micropython python3
boost-python ipython python wxpython
boost-python@1.59 ipython@5 python-markdown zpython
==> Searching taps on GitHub...
caskroom/cask/awips-python caskroom/cask/mysql-connector-python
caskroom/cask/kk7ds-python-runtime
==> Searching blacklisted, migrated and deleted formulae..
2、这时候看到python3了，然后执行 brew install python3
如果成功你会看到最后几行：
They will install into the site-package directory
/usr/local/lib/python3.6/site-packages
See: https://docs.brew.sh/Homebrew-and-Python.html
==> Summary
�� /usr/local/Cellar/python3/3.6.4_2: 3,593 files, 56.2MB
/usr/local/Cellar/python3/3.6.4_2 这是路径，你可以打开看下：
3、这时候安装完成了，你可以在终端输入 python3和 python，然后你就会发现你同时拥有了2，3版本。
zhangyudeiMac:~ zhangyu$ python3
Python 3.6.4 (default, Jan 6 2018, 11:51:59)
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.39.2)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>
zhangyudeiMac:~ zhangyu$ python
Python 2.7.10 (default, Jul 15 2017, 17:16:57)
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.31)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>
