Configuring Our Virtual Environment

In this lesson we’ll set up the tools and configure a Python virtual environment to isolate project dependencies and streamline development. For details on the built-in venv module see the official docs: https://docs.python.org/3/library/venv.html.

Why use a virtual environment?

Isolates a project’s dependencies from the system Python and from other projects.
Lets different projects use different package or Python versions (for example, one project can use OpenCV 4.x while another uses 3.x). See OpenCV: https://opencv.org/
Makes projects portable: export dependencies with a requirements file and others can recreate the environment exactly using pip install -r requirements.txt. See pip requirements docs: https://pip.pypa.io/en/stable/topics/requirements-files/

Editor tooling (example: VS Code)

Use editor extensions to speed development and reduce boilerplate. Popular choices include GitHub Copilot, GitHub Copilot Chat, Blackbox, and Tabnine.
When you enable GitHub Copilot you will authenticate through GitHub.
You can toggle auto-complete and other extension features depending on how much in-editor assistance you want.

Sample Flask routes (example code you might develop inside your virtual environment)

from flask import Flask, request, redirect
import uuid

app = Flask(__name__)
todos = []

@app.route('/create-todo', methods=['POST'])
def create_todo():
    newTodo = {
        "id": str(uuid.uuid4()),
        "title": request.form['title'],
        "completed": False
    }
    todos.append(newTodo)
    return redirect('/')

@app.route('/update-todo/<id>')
def update_todo(id):
    todo = [t for t in todos if t['id'] == id][0]
    todo['completed'] = not todo['completed']
    return redirect('/')

@app.route('/delete-todo/<id>')
def delete_todo(id):
    todo = [t for t in todos if t['id'] == id][0]
    todos.remove(todo)
    return redirect('/')

if __name__ == '__main__':
    app.run()

Creating a Python virtual environment Open a terminal in your project directory (for example, imageoptimizer) and run:

python3 -m venv venv

Notes on naming

The venv folder can be named anything (image-optimizer, venv, myenv). Many teams use venv for consistency and to simplify .gitignore rules.
The command above creates a venv directory containing an isolated Python interpreter, pip, and site-packages for that environment.

Activate the virtual environment Use the activation command appropriate for your shell and OS. The table below lists common commands:

Platform / Shell	Activation command
macOS / Linux (bash/zsh)	`source venv/bin/activate`
macOS / Linux (fish)	`source venv/bin/activate.fish`
macOS / Linux (csh / tcsh)	`source venv/bin/activate.csh`
Windows (PowerShell)	`venv\Scripts\Activate.ps1`
Windows (cmd.exe)	`venv\Scripts\activate.bat`

After activation your prompt typically shows the environment name:

(venv) $ python --version
Python 3.12.6

When activated, the python and pip commands refer to the virtual environment’s binaries; you no longer need to run python3 explicitly. What the venv folder contains (overview) Inside the created venv directory you will commonly find:

bin/ (macOS/Linux) or Scripts\ (Windows) — executables and activation scripts
include/ — C headers used when compiling extension modules
lib/ or Lib\ — installed Python packages
pyvenv.cfg — configuration for the virtual environment

Example snippet from an activate script for csh (truncated and illustrative)

# This file must be used with "source bin/activate.csh" *from csh*.
# Created by Davide Di Blasi <davidedb@gmail.com>.
setenv VIRTUAL_ENV "/Users/jeremy/Projects/genaiocourse/imageoptimizer/venv"
set _OLD_VIRTUAL_PATH="$PATH"
setenv PATH "$VIRTUAL_ENV/bin:$PATH"

Working with dependencies

Install packages inside the activated venv:

pip install opencv-python requests

Freeze the current environment to a requirements.txt for reproducibility:

pip freeze > requirements.txt

Recreate the environment elsewhere:

pip install -r requirements.txt

Add your virtual environment directory (for example, venv/) to .gitignore so installed packages are not committed to source control.

Do not commit your virtual environment directory to Git. Instead commit requirements.txt (or a lock file) so collaborators can recreate the environment reliably.

Summary

A Python virtual environment isolates dependencies per project so multiple projects can use different package or Python versions.
Create a venv with python3 -m venv venv, activate it with the proper activation script for your shell/OS, then install packages using pip.
Export dependencies with pip freeze > requirements.txt and recreate environments with pip install -r requirements.txt.
Editor extensions (e.g., GitHub Copilot, Tabnine) can speed development but do not change how virtual environments work.

Links and references

Python venv documentation: https://docs.python.org/3/library/venv.html
pip requirements files: https://pip.pypa.io/en/stable/topics/requirements-files/
VS Code: https://code.visualstudio.com/
OpenCV: https://opencv.org/

Course Introduction

Introduction to AI-Assisted Development

Planning Phase

Development Phase - Backend

Development Phase - Frontend

Project Completion

Configuring Our Virtual Environment

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