CentOS-7 install pip

First need to install epel-release expansion source

python2.7 corresponding to pip
python3.x corresponding to pip3ui

yum -y install epel-release

(1)随后，清空cache，并makecache

yum clear all
yum makecache

(2)安装pip 

yum -y install python-pip

(3)升级pip

pip install --upgrade pip