Venv Creation

cd ~/app python -m venv env source env/bin/activate

This creates a virtual Environment of Python, venv allows package isolation and non interference with development machine.

pip install --upgrade pip

Update pip as good security measure
Install required packages.

pip install pewpew

* The most popular way is package method, lets take an example of flask app. 
* ├── app
│   ├── __init__.py
│   └── views.py
├── env
├── requirements.txt
└── run.py
* to create requirements, 
* `pip freeze > requirements.txt`