centos7 安装python3，与python2.7并存

      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
     cd ~
     ls
     wget https://www.python.org/ftp/python/3.6.2/Python-3.6.2.tar.xz
     mkdir /usr/local/python3 
     tar -xvJf  Python-3.6.2.tar.xz
     cd Python-3.6.2
     ./configure --prefix=/usr/local/python3
     make && make install
     ln -s /usr/local/python3/bin/python3 /usr/bin/python3
     ln -s /usr/local/python3/bin/pip3 /usr/bin/pip3
     python
     python3
     history