Centos7安装python3，python2共存

20200609

centos7增加python3版本环境

一、旧版本信息

[root@mysql_master 17:00:23]:/usr/libexec
#python
Python 2.7.5 (default, Aug  7 2019, 00:51:29) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-39)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> 

二、注意事项

切记不可随意删除系统自带python版本，因为系统有很多软件依赖着

三、安装办法

yum
手动下载并编译python源代码安装

3.1源码安装教程

3.1.1.下载安装包和安装依赖

cd /usr/local/src
wget https://www.python.org/ftp/python/3.6.8/Python-3.6.8.tgz
yum install zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel gcc make

3.1.2.解压安装包

tax -xvf Python-3.6.8.tgz

3.1.3安装指定版本python

3.1.3.1.预配置

./configure --prefix=/usr/local/python3.6.8 --with-ssl

3.1.3.1.编译安装

sudo make
sudo make install 

3.1.4.删除就版本python默认软链指向

1.查看python现有信息

2.重命名旧的python软链
mv /usr/bin/python /usr/bin/python.bak
mv /usr/bin/pip /usr/bin/pip.bak
3.建立python新软链和pip软链
ln -s /usr/local/python3.6.8/bin/python3 /usr/bin/python368
ln -s /usr/local/python3.6.8/bin/pip3 /usr/bin/pip
4.测试版本
root@chenwx:/usr/bin# python
Python 3.6.8 (default, Jun  9 2020, 14:37:48) 
[GCC 7.5.0] on linux
Type "help", "copyright", "credits" or "license" for more information.

3.1.5.指定默认python版本

如上步操作所示，已经制定python3.6.8版本是默认python版本

3.1.6.使用alternatives 来为整个系统更改Python版本

alternatives --install /usr/bin/python python /usr/bin/python2.7 1
alternatives --install /usr/bin/python python /usr/bin/python3.6 2
alternatives --install /usr/bin/pip pip /usr/bin/pip2.7 1
alternatives --install /usr/bin/pip pip /usr/local/bin/pip3.6 2
设置默认版本
alternatives --config python

四.切换python3委默认后yum出问题解决

vim /usr/libexec/urlgrabber-ext-down
vi /usr/bin/yum
首行的#! /usr/bin/python	
都改为#! /usr/bin/python2.7
firewall-cmd也需要手工设置一下
# vim /usr/bin/firewall-cmd

首行改为
#!/usr/bin/python2.7 -Es