在CentOS7下，默认安装的就是python2.7，我现在来教大家如何安装python3：

1、首先安装python3.6可能使用的依赖

# yum -y install openssl-devel bzip2-devel expat-devel gdbm-devel readline-devel zlib-devel

2、下载python源码包，地址为https://www.python.org/downloads/source/，然后通过xftp上传上去，或者直接使用wget命令，wget https://www.python.org/ftp/python/3.6.1/Python-3.6.1.tgz下载到本地

# tar -zxvf Python-3.6.1.tgz# cd Python-3.6.1/

3、把python3.6安装到/usr/local目录下

# ./configure --prefix=/usr/local/  # make  # make altinstall

4、更改/usr/bin/python链接

# cd /usr/bin  # mv python python.backup  # ln -s /usr/local/bin/python3.6 /usr/bin/python  # ln -s /usr/local/bin/python3.6 /usr/bin/python3  # rm -rf /usr/bin/python2  # ln -s /usr/bin/python2.7 /usr/bin/python2

5、更改yum脚本的python依赖

# cd /usr/bin  # ll yum*

有以下文件：

-rwxr-xr-x 1 root root   802 Jan  2 17:53 yum  -rwxr-xr-x 1 root root  9374 Jan  2 17:53 yum-builddep  -rwxr-xr-x 1 root root  8091 Jan  2 17:53 yum-config-manager  -rwxr-xr-x 1 root root  7610 Jan  2 17:53 yum-debug-dump  -rwxr-xr-x 1 root root  7904 Jan  2 17:54 yum-debug-restore  -rwxr-xr-x 1 root root 10906 Jan  2 17:54 yumdownloader  -rwxr-xr-x 1 root root 11032 Jan  2 17:54 yum-groups-manager

修改以上文件头：#!/usr/bin/python 改为 #!/usr/bin/python2

可以安装一个tree测试一下

# yum -y install tree

如果出现以下报错：File “/usr/libexec/urlgrabber-ext-down”, line 28

vim /usr/libexec/urlgrabber-ext-down

将/usr/bin/python改为/usr/bin/python2即可

这样，yum安装软件的时候就不会报错了，而且默认安装的就是python3了，输入python时，就会进入python3界面，如果想进入python2，那么就输入python2好了。