Flask Tutorial: Build a Python Website from Scratch
Table of Contents
- Introduction
- Prerequisites
- Install Flask
- Create the Project Structure
- Build Your First Route
- Add HTML Templates
- Handle a Simple Form
- Recommended Project Structure
- Next Steps
Introduction
Flask is a lightweight Python web framework that is friendly for beginners but flexible enough for real applications. It gives you routing, request handling, templates, and extension support without forcing a large project structure from day one.
In this tutorial, you will create a small Flask website from scratch. The goal is not to build a huge production app immediately, but to understand the core building blocks: routes, templates, forms, and project organization.
Prerequisites
Before starting, make sure you have:
- Python 3 installed
- basic Python knowledge
- a terminal or command prompt
- a code editor
You can check your Python version with:
python --versionDepending on your system, you may need to use python3 instead of python.
Install Flask
Create a new folder for your project:
mkdir my_flask_app
cd my_flask_appThen create and activate a virtual environment:
python -m venv .venvOn macOS or Linux:
source .venv/bin/activateOn Windows:
.venv\Scripts\activateInstall Flask:
pip install FlaskCreate the Project Structure
Start with a simple structure:
my_flask_app/
└── app.pyCreate app.py and add your first Flask application.
Build Your First Route
from flask import Flask
app = Flask(__name__)
@app.route("/")
def home():
return "Hello, Flask!"
if __name__ == "__main__":
app.run(debug=True)Run the app:
python app.pyOpen this URL in your browser:
http://127.0.0.1:5000/You should see:
Hello, Flask!Add HTML Templates
Returning plain text is useful for testing, but real websites need HTML. Flask uses Jinja templates by default.
Update your structure:
my_flask_app/
├── app.py
└── templates/
└── home.htmlCreate templates/home.html:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Home</title>
</head>
<body>
<h1>Hello, Flask!</h1>
<p>Welcome to your first Flask website.</p>
</body>
</html>Update app.py:
from flask import Flask, render_template
app = Flask(__name__)
@app.route("/")
def home():
return render_template("home.html")
if __name__ == "__main__":
app.run(debug=True)Refresh the browser and Flask will render the template.
Handle a Simple Form
Add a basic route that accepts a name:
from flask import Flask, render_template, request
app = Flask(__name__)
@app.route("/", methods=["GET", "POST"])
def home():
name = None
if request.method == "POST":
name = request.form.get("name")
return render_template("home.html", name=name)Update home.html:
<form method="post">
<label for="name">Your name</label>
<input id="name" name="name" type="text">
<button type="submit">Submit</button>
</form>
{% if name %}
<p>Hello, {{ name }}!</p>
{% endif %}Jinja lets you pass data from Python into HTML safely and clearly.
Recommended Project Structure
As the project grows, avoid putting everything in one file. A slightly better starter structure looks like this:
my_flask_app/
├── app.py
├── templates/
│ └── home.html
└── static/
└── style.cssFor larger apps, you can later learn about blueprints, configuration files, database models, migrations, and testing.
Next Steps
You now have the foundation of a Flask website:
- Flask installed in a virtual environment
- a route that responds to browser requests
- an HTML template rendered by Flask
- a basic form handled with
request.form - a project structure that can grow gradually
From here, try adding a second page, styling it with CSS, and connecting a database with SQLAlchemy.
Related Articles
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Flask Jinja Templates: Layouts, Variables, and Loops
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Flask Routing: URLs, Requests, and Responses
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Flask Tutorial: Setup and First Route
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