Python3 与 Python2共存

1. 查看当前python版本

   python --version

2. 备份python

   which python
   mv /usr/bin/python /usr/bin/python.bak

3. 下载安装更新python3

   wget https://www.python.org/ftp/python/3.6.2/Python-3.6.2.tar.xz
   tar -xvJf  Python-3.6.2.tar.xz

4. 安装关联程序，安装编译python3

   yum install -y zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel gcc make
   cd Python-3.6.2
   ./configure prefix=/usr/local/python3
   make && make install
   ln -s /usr/local/python3/bin/python3 /usr/bin/python

5. 查看python版本

   python --version

6. 修改相关执行程序python版本

   vi /usr/bin/yum
   把#! /usr/bin/python修改为#! /usr/bin/python2
   vi /usr/libexec/urlgrabber-ext-down 
   文件里面的#! /usr/bin/python 也要修改为#! /usr/bin/python2