📘 Introduction to Flask — A Complete Beginner’s Guide

A clean, minimal, and hands-on learning journey into Flask, the lightweight and flexible Python web framework. This repository mirrors a real-world development setup — from environment to project organization — for building scalable Flask apps step by step.

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🚀 What is Flask?

Flask is a micro web framework for Python.

• Lightweight and minimal
• Flexible structure — you define your architecture
• Easy to learn and perfect for beginners
• Extensible with a rich ecosystem of third-party tools

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⚔️ Flask vs Django — What's the Difference?

Feature	Flask	Django
Design	Micro-framework (minimal core)	Full-stack framework
Structure	Developer-defined (flexible)	Convention-based (pre-defined)
Admin UI	Not included by default	Built-in admin panel
Best For	APIs, small apps, rapid prototyping	Large-scale feature-rich apps
Learning Curve	Simple & beginner-friendly	Steeper but comprehensive

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🛠️ Project Setup

📁 Step 1: Create Project Directory

mkdir Flask-Learning && cd Flask-Learning\app

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🐍 Step 2: Create and Activate Virtual Environment

python -m venv MyEnvironment

✅ Activate (PowerShell)

.\MyEnvironment\Scripts\Activate.ps1

or

.\Flask-Learning\MyEnvironment\Scripts\Activate.ps1

To deactivate:

deactivate

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📦 Step 3: Install Flask Inside Virtual Environment

pip install flask

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📂 Project Structure

Flask-Learning/
│
├── app/                                # Core application folder
│   ├── app.py                          # Entry point that initializes and runs the Flask app
│
│   ├── controllers/                    # Handles route logic using Blueprints (modular routing)
│   │   └── welcome_controller.py       # Blueprint for handling the '/' route (e.g., Welcome page)
│
│   ├── services/                       # Business logic abstraction layer
│   │   └── welcome_service.py          # Contains logic for managing and returning welcome-related data
│
│   └── templates/                      # Jinja2 templates for rendering dynamic HTML content
│       └── Welcome.html                # Template that uses variables (e.g., name, names list)
│
├── MyEnvironment/                      # Virtual environment 
├── .gitignore                          # Excludes virtual environment and cache/temp files
└── Readme.md                           # Project documentation and learning progress

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▶️ How to Run the Flask Server

Once you're inside the virtual environment and at the root of your project:

python app.py

By default, Flask will run on:

http://127.0.0.1:5000

If you've set a custom host and port (like 0.0.0.0:3000), Flask will reflect that in the terminal when the server starts.

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📚 Topics Covered

1. Setting up Flask with a virtual environment
2. Installing and configuring Flask
3. Rendering static and dynamic content using Jinja2 templates
4. Structuring Flask apps cleanly with folders like templates/, controllers/, and services/
5. Using Blueprints to modularize routes
6. Creating a Service Layer to manage business logic separately
7. Sending data (variables, lists) from Python to HTML

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🔗 What’s Next?

1. This marks the end of the Flask learning phase..
2. 🧠 Now continuing the journey by building a real-world >ToDo App using Flask.. 👉 Follow my next repo here ➜ Flask-ToDo-App (https://github.com/Madhav-P-2005/Flask-ToDo-App.git)

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📚 References

• Flask Official Docs
• Jinja2 Templates
• Flask GitHub Repo

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Happy Coding 🧪✨