Use venv to create a directory called "venv" that holds all the dependencies and stuff
python -m venv venv
Activate th venv for this shell.
source venv/bin/activate
You can deacvate it with just
deacvate
With the venv active, just install things with pip
pip install numpy
When you add dependencies, update the requirements file with. Add this to git
pip freeze > requirements.txt
On a new machine, you will want to reacrate the venv with the requirements.txt file by combining the stuff above
python -m venv venv && source venv/bin/activate && pip install -r requirements.txt