1. sudo rm /usr/local/bin/python
sudo ln -s /usr/bin/python3.6 /usr/local/bin/python
------- python 2.x 切换为 Python3.x
2. sudo rm /usr/local/bin/python
sudo ln -s /usr/bin/python2.7 /usr/local/bin/python
---------python 3.x 切回 Python2.x
Ubuntu 下 python2.7 和 Python3.x 切换
原文：http://www.cnblogs.com/dongtian/p/6604574.html