centos7安装pip
1.执行:yum install python-pip
若没有python-pip包，先执行：yum -y install epel-release，再执行yum install python-pip
2.pip install --upgrade pip
centos默认安装了python2.7
1.mkdir /usr/local/python3
2.安装依赖包：
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
3.在/usr/local/python3目录下
wget https://www.python.org/ftp/python/3.6.2/Python-3.6.2.tar.xz
4.在/usr/local/python3目录下
tar -xvf Python-3.6.2.tar.xz
cd Python-3.6.2
./configure --prefix=/usr/local/python3
make && make install
5.切换到/usr/bin/目录下
mv python python.bak
mv pip pip.bak
ln -s /usr/local/python3/bin/python3 /usr/bin/python
ln -s /usr/local/python3/bin/pip3 /usr/bin/pip
6.防止以后用yum源安装软件时，报错
vi /usr/bin/yum
输入i，把文件开头第一行的
#!/usr/bin/python改成#!/usr/bin/python2.7
vi /usr/libexec/urlgrabber-ext-down
输入i，把文件开头第一行的
#!/usr/bin/python改成#!/usr/bin/python2.7
7.验证
输入python，进入python3.6.2
输入python2，进入python2.7
