Building a Simple Web Application with Flask

Building a Simple Web Application with Flask

Step-by-Step Guide: Building a Simple Web Application with Flask

🛠 Prerequisites

Python installed on your machine (Python 3.7+ recommended)


Basic knowledge of Python


Text editor (e.g., VS Code, Sublime Text)


Terminal or command prompt


📁 1. Project Setup

Create a project folder:


bash

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Edit

mkdir flask_app

cd flask_app

Create a virtual environment (optional but recommended):


bash

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python -m venv venv

source venv/bin/activate  # On Windows use: venv\Scripts\activate

Install Flask:


bash

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pip install flask

🧱 2. Create a Basic Flask Application

Inside the flask_app folder, create a file named app.py.


Add the following code:


python

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from flask import Flask


app = Flask(__name__)


@app.route('/')

def home():

    return "Hello, Flask!"


if __name__ == '__main__':

    app.run(debug=True)

▶ 3. Run the Application

Run the app from the terminal:


bash

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python app.py

Open your browser and go to http://127.0.0.1:5000/. You should see:


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Hello, Flask!

🌐 4. Add an HTML Template

Create a folder named templates.


Inside templates, create a file named index.html:


html

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<!DOCTYPE html>

<html>

<head>

    <title>Flask App</title>

</head>

<body>

    <h1>Welcome to My Flask App</h1>

</body>

</html>

Modify your app.py to render this template:


python

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from flask import Flask, render_template


app = Flask(__name__)


@app.route('/')

def home():

    return render_template('index.html')


if __name__ == '__main__':

    app.run(debug=True)

📨 5. Add a Form Example

To add a simple form and process input:


Update index.html:


html

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<h1>Enter Your Name</h1>

<form action="/greet" method="POST">

    <input type="text" name="username">

    <input type="submit" value="Greet Me">

</form>

Update app.py:


python

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from flask import Flask, render_template, request


app = Flask(__name__)


@app.route('/')

def home():

    return render_template('index.html')


@app.route('/greet', methods=['POST'])

def greet():

    name = request.form.get('username')

    return f"Hello, {name}!"


if __name__ == '__main__':

    app.run(debug=True)

✅ What You've Learned

Setting up a Flask app


Creating routes


Rendering HTML templates


Handling form input

⏭️ What's Next?

Add CSS/JavaScript for front-end styling


Connect to a database (e.g., SQLite, PostgreSQL)


Explore Flask extensions like Flask-WTF, Flask-SQLAlchemy


Would you like help adding a database or deploying this to the web (e.g., on Heroku or Render)?

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