Python Flask introduction

1. What is Flask?

Flask is a small and simple web framework for Python.

In simple words:
👉 Flask helps you create websites using Python
👉 It is used to build web apps and APIs
👉 It is easy to learn and beginner-friendly

2. What is a Web Framework?

A web framework:

• Handles web requests

• Sends responses to browser

• Saves you from writing everything from scratch

Flask does all this in a simple way.

3. Why Use Flask?

Flask is popular because:
✔ Very easy to learn
✔ Less code
✔ Flexible
✔ Perfect for beginners
✔ Used in real projects

4. Flask vs Django (Very Simple)

👉 Start with Flask if you are new.

5. Install Flask

Run this command in terminal:

6. Create Your First Flask App

This is the smallest Flask program.

Example

7. How This Code Works (Simple Explanation)

👉 Start the server

8. Open Flask App in Browser

After running the file, open browser and go to:

9. Add Another Page (Route)

Example

10. Flask with HTML Content

Flask can send HTML to browser.

Example

11. Dynamic URL (User Name)

Example

Open:

Output:

12. Flask for API (JSON Response)

Example

👉 Used in mobile apps & frontend apps.

13. Debug Mode (For Development)

Example

👉 Automatically reloads on code change.

14. Real-World Uses of Flask

Flask is used to build:
✔ Small websites
✔ REST APIs
✔ Admin panels
✔ Backend for mobile apps
✔ Automation dashboards

15. Common Beginner Mistakes

❌ Forgetting to install Flask
❌ Not saving file before running
❌ Running wrong Python file
❌ Not using debug mode

16. Simple Practice Examples

Example 1: Greeting App

Example 2: Age App

Example 3: Status Page

17. Flask Learning Path (Easy)

1️⃣ Learn Python basics
2️⃣ Learn Flask routes
3️⃣ Learn HTML
4️⃣ Learn forms & database
5️⃣ Build small projects

18. Summary (Python Flask Introduction)

✔ Flask is a Python web framework
✔ Easy and lightweight
✔ Perfect for beginners
✔ Used in real-world apps
✔ Great start for web development

📘 Perfect for Beginner Python Web eBook

This chapter is ideal for:

• Python learners

• Web development beginners

• Backend starters

• Project-based learning

If you want next, I can write:

• Flask Routing (Deep)

• Flask Templates (HTML)

• Flask Forms

• Flask + Database

• Flask Mini Projects

Just tell me 😊