1.centos7自带python2.7的环境。下面开始安装python3.6.3（说明：可以whereis python 看到python的所在路径）
2.安装依赖包,执行如下2条命令
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
3.下载python。（说明：我下载的是python3.6.3，如想下载3.6.X版本，自行修改）
wget https://www.python.org/ftp/python/3.6.3/Python-3.6.3.tgz
4.解压
tar -zxf Python-3.6.3.tgz
5.进入到解压好的Python-3.6.3文件夹中
cd Python-3.6.3
6.执行如下两条命令
./configure --prefix=/usr/bin/python3.6.3 make && make install
7.创建软连接
ln -s /usr/bin/python3.6.3/bin/python3 /usr/bin/python3
8.查看python3.6.3是否安装成功
python3 -v