virtualenv

Which Python

Literally V3 or V2.7

sudo pip install virtualenv
virtualenv --version

virtualenv --python $(which python3.6) ~/.virtualenvs/chalice-demo
source ~/.virtualenvs/chalice-demo/bin/activate
pip install arbirary-package

When you’ve finished.

deactivate
pip freeze > requirements.txt

Then later…

pip install -r requirements.txt