Centos7.7下安装Python3.7 并兼容python2.7

前言

1.首先来看一下系统版本

[root@python3 ~]# cat /etc/redhat-release
CentOS Linux release 7.7.1810 (Core)

2.更新一下yum源，yum源我这里用的都是阿里云的源

[root@python3 ~]# cd /etc/yum.repos.d/

[root@python3 yum.repos.d]# mkdir bak

[root@python3 yum.repos.d]# mv * bak

[root@python3 yum.repos.d]# wget http://mirrors.aliyun.com/repo/Centos-7.repo

[root@python3 yum.repos.d]# wget http://mirrors.aliyun.com/repo/epel-7.repo

3.安装python3.7之前需要先安装一些依赖，，这也是上面更新yum源的原因

[root@python3 ~]# yum -y install zlib-devel bzip2-devel openssl-devel openssl-static ncurses-devel sqlite-devel readline-devel tk-devel gdbm-devel db4-devel libpcap-devel xz-devel libffi-devel lzma gcc

[root@python3 ~]# yum -y groupinstall "Development tools"

yum -y install gcc
yum install zlib* -y
yum -y install libffi-devel tk-devel
yum install mysql-devel

不安装也有可能不会报错，但是安装了一定不会报错，安不安装自己把握。

4.下载python3.7安装包，方法很多，我这里直接用wget从官网上下载

[root@python3 ~]# cd /usr/local/src/

[root@python3 src]# wget https://www.python.org/ftp/python/3.7.0/Python-3.7.0.tar.xz

将安装包下载到/usr/local/src/目录下

5.解压&&移动

[root@python3 src]# tar xvf Python-3.7.0.tar.xz

[root@python3 src]# mv Python-3.7.0 /usr/local/python-3.7

[root@python3 src]# cd /usr/local/python-3.7/

6.安装&&编译

[root@python3 python-3.7]# ./configure --prefix=/usr/local/sbin/python-3.7

将python3.7安装到/usr/local/sbin/python-3.7目录下

[root@python3 python-3.7]# make && make install

安装完成后，若出现以下两行，说明安装成功；

Installing collected packages: setuptools, pip
Successfully installed pip-10.0.1 setuptools-39.0.1

7.安装成功之后就能使用了

[root@python3 python-3.7]# /usr/local/sbin/python-3.7/bin/python3
Python 3.7.0 (default, Mar 15 2019, 00:44:37)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-36)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

【此处退出的命令 exit()】

虽然能用了，但是命令较长使用起来并不方便,we konw 系统本身是带的有python的，看一下版本

[root@python3 ~]# python -V

Python 2.7.5

8.看一下python命令的绝对路径

[root@python3 ~]# which python

/usr/bin/python

[root@python3 ~]# ll /usr/bin/ |grep python

-rwxr-xr-x. 1 root root 11312 Nov 14 00:00 abrt-action-analyze-python
lrwxrwxrwx. 1 root root 7 Mar 14 18:19 python -> python2
lrwxrwxrwx. 1 root root 9 Mar 14 18:19 python2 -> python2.7
-rwxr-xr-x. 1 root root 7216 Oct 31 07:46 python2.7

可以看到python命令是通过软链接连接到python2.7的，[做运维的小年轻]那我们现在安装了python3.7，是不是可以将python命令做一个软链接链接到python3，答案是肯定的昂。

9.将python命令通过软链接指向到python3命令（就是上面那一大串/usr/local/sbin/python-3.7/bin/python3）

[root@python3 ~]# rm -rf /usr/bin/python

[root@python3 ~]# ln -sv /usr/local/sbin/python-3.7/bin/python3 /usr/bin/python

‘/usr/bin/python’ -> ‘/usr/local/sbin/python-3.7/bin/python3’

[root@python3 ~]# ll /usr/bin/ |grep python

-rwxr-xr-x. 1 root root 11312 Nov 14 00:00 abrt-action-analyze-python
lrwxrwxrwx. 1 root root 38 Mar 14 19:24 python -> /usr/local/sbin/python-3.7/bin/python3
lrwxrwxrwx. 1 root root 9 Mar 14 18:19 python2 -> python2.7
-rwxr-xr-x. 1 root root 7216 Oct 31 07:46 python2.7

10.查看现在的默认版本

[root@python3 ~]# python -V
Python 3.7.0

11.修改完python默认版本之后，会存不能执行yum命令，需要做一些修改，如下：

①Vim /usr/bin/yum：

!/usr/bin/python  改成  !/usr/bin/python2.7 

②Vim /usr/libexec/urlgrabber-ext-down：

/usr/bin/python  改为   /usr/bin/python2.7

③Vim /usr/bin/yum-config-manager

#!/usr/bin/python 改为 #!/usr/bin/python2.7  

12.最后将pip指向到python3.7

[root@python3 ~]# ln -sf /usr/local/sbin/python-3.7/bin/pip3 /usr/bin/pip

[root@python3 ~]# pip --version
pip 10.0.1 from /usr/local/sbin/python-3.7/lib/python3.7/site-packages/pip (python 3.7)

大功告成。