linux默认的python版本是2.7的版本，但想要用3.x的版本，又不能每次都输入python3

# python
Python 2.7.5 (default, Oct 14 2020, 14:45:30) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-44)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> 

python3

# python3
Python 3.6.8 (default, Oct 13 2020, 16:18:22) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-44)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> exit
Use exit() or Ctrl-D (i.e. EOF) to exit
>>> 

所以，想要更改默认的python的版本指向

切换到root用户，更改两个python的优先级，当然如果你安装的python不在默认路径下，要指向具体的路径。

# update-alternatives --install /usr/bin/python python /usr/bin/python2 100
# update-alternatives --install /usr/bin/python python /usr/bin/python3 150

此时，输入python就是所需要的版本

# python
Python 3.6.8 (default, Oct 13 2020, 16:18:22) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-44)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>