由于centos7原本就安装了Python2，而且这个Python2不能被删除
首先安装python3环境依赖包
yum -y groupinstall "Development tools"
yum -y install zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel gdbm-devel db4-devel libpcap-devel xz-devel
下载python3
wget https://www.python.org/ftp/python/3.6.2/Python-3.6.2.tar.xz
建立python3文件夹
mkdir /usr/local/python3
解压
tar -zxvf Python-3.6.2.tar.xz
cd Python-3.6.2
./configure --prefix=/usr/local/python3
make && make install
最后两条命令运行
ln -s /usr/local/python3/bin/python3 /usr/bin/python3
ln -s /usr/local/python3/bin/pip3 /usr/bin/pip3
测试有没有安装成功，如图可以看到环境共存，安装成功。
，如
