Create python virtualenv in a dir for python3
$ cd codefolder
$ python3 -m venv venv
(or, $ virtualenv -p python3 . )
Start your virtualenv again
$ source yourvenv/bin/activate
Exit python virtualevn
$ deactivate
Shorthand to create virtualenv and folder
$ virtualenv yourvenv -p python3
Install django
$ pip install django==3.1.5