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