how to make default python version in linux code example

Example 1: linux set python 3 as default

1. Check current version:
$ python --version
2. get root permissions:
$ sudo su
3. set python3 as default:
$ update-alternatives --install /usr/bin/python python /usr/bin/python3 1
4. Done. (Check by $ python --version)

Example 2: how to change python version on linux

#Check available versions
ls /usr/bin/python*
#Change the used version 3.5 or 3.7 etc
alias python='/usr/bin/python3.x'
#do this other thing
. ~/.bashrc
#Check version 
python --version