create python evn from requirements.txt code example

Example 1: python virtual environment

python3 -m venv env
python -m virtualenv env #py2

source env/bin/activate

#all this is on same directory

Example 2: .env tutorial

const express = require('express');const app = express();const port = process.env.PORT || 3000;require('dotenv').config();app.get('/', (req, res) => {    res.send(process.env.SECRET_KEY);})app.listen(port, () => {    console.log(`Server is running on port ${port}.`)})