Flask is a micro web framework written in Python. It’s called “micro” not because it’s limited, but because it keeps the core simple and extensible. You can build anything from a small prototype to a full-featured web application. Flask doesn’t impose strict requirements on project structure or dependencies. Here is a list of some features.

• Routing: Easily map URLs to Python functions using the @app.route() decorator.
• Templates: Use Jinja2 templating to dynamically generate HTML (render_template()).
• Request Handling: Access query parameters, form inputs, JSON data with request.
• Modular: Add only what you need — like SQLAlchemy for database handling or Flask-Login for authentication.
• Debug Mode: Built-in development server with real-time reloading and error reporting.

🔹 Part 1: Setup Python and Flask

✅ Step 1: Install Python (only once, and only if its not already installed)

1. Go to the official Python website: 👉 https://www.python.org/downloads
2. Click the yellow download button that says “Download Python 3.x.x”.
3. IMPORTANT: Check the box that says Add Python to PATH before clicking Install Now.
4. When it’s done, restart your computer (just in case!).

✅ Step 2: Open the Terminal

1. Press Windows key, type cmd, and hit Enter.
2. You’ll see a black window — this is the Command Prompt. You’re ready to talk to your computer 💬

✅ Step 3: Install Flask

In the Command Prompt window, type this:

pip install flask

Wait a moment — it will install Flask. You’ll see a bunch of lines. If it ends without errors, you’re good!

🔹 Part 2: Create Your Web App

✅ Step 4: Create a New Folder

1. On your desktop, right-click > New > Folder → Name it flask_hello
2. Open it, and right-click inside → New > Text Document
3. Rename it to: app.py (make sure it’s not app.py.txt)

✅ Step 5: Write Your Python Web App

1. Right-click app.py → Open with → Notepad (or Notepad++)
2. Copy & paste this code:

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello():
    return 'Hello, World! This is my first web app!'

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

Click File > Save

🔹 Part 3: Run Your Webpage

✅ Step 6: Run Your Flask App

Back in your Command Prompt, type:

cd Desktop\flask_hello

Then type:

python app.py

You will see in the command prompt

Running on http://127.0.0.1:5000/

✅ Step 7: View It in the Browser

1. Open your browser (Edge, Chrome, etc.)
2. Type in the address bar: 👉 http://127.0.0.1:5000/
3. 🎉 You’ll see: “Hello, World! This is my first web app!”

You just ran a tiny server on your own computer. Flask gave you a webpage when you went to a URL (localhost). You can now create more routes (pages), or templates (HTML files), step by step!

Flask_Hello_World_Guide.docx by ChatGPT