Python can be configured via alternatives on CentOS
List available versions ...
# alternatives --list | grep -i python...and set it
# alternatives --config python
There are 2 programs which provide 'python'.
Selection Command
-----------------------------------------------
*+ 1 /usr/libexec/no-python
2 /usr/bin/python3
3 /usr/bin/python2
Enter to keep the current selection[+], or type selection number: 2
# python -V
Python 3.6.8