[python] change python version

sudo update-alternatives --config python3

There are 2 choices for the alternative python3 (providing /usr/bin/python3).

  Selection    Path                Priority   Status
------------------------------------------------------------
  0            /usr/bin/python3.7   2         auto mode
  1            /usr/bin/python3.6   1         manual mode
* 2            /usr/bin/python3.7   2         manual mode

Press <enter> to keep the current choice[*], or type selection number: 

https://dev.to/alfchee/how-to-switch-between-python-3-versions-5gh6

How to switch between Python 3 versions