Project Structure
A basic Flask project typically has the following structure:
project_name/
app.py
templates/
index.html
static/
- app.py: Contains the Flask application code.
- templates: Stores HTML templates.
- static: Stores static files like CSS, JavaScript, and images.
Core Components
- Import Flask:
- Python
from flask import Flask, render_template
- Create Flask app instance:
- Python
app = Flask(__name__)
- Define routes:
- Python
@app.route('/')
def index():
return render_template('index.html')
- Create templates:
- HTML
<!DOCTYPE html>
<html>
<head>
<title>Hello, World!</title>
</head>
<body>
<h1>Hello, World!</h1>
</body>
</html>
- Run the application:
- Python
if __name__ == '__main__':
app.run(debug=True)
Explanation:
- The
@app.route('/')
decorator maps the functionindex()
to the root URL (/
). - The
render_template()
function renders theindex.html
template. - The
debug=True
argument enables debug mode for easier development.
Additional Features
- Handling user input: Use
request.args
orrequest.form
to access data from HTML forms. - Redirects: Use
redirect()
to redirect users to different URLs. - Error handling: Use
@app.errorhandler()
to handle specific error types. - Sessions: Store user data across requests using
session
.
By understanding these core components and concepts, you can build simple web applications with Flask.
Building a Simple Web Application
What are the basic components of a Flask application?
App instance, routes, views, and templates.
How do I define a route in Flask?
Use the @app.route()
decorator.
What is the role of the render_template
function?
Renders HTML templates with dynamic content.
What is the recommended project structure for a Flask application?
A common structure includes app.py, templates, and static folders.
Where should I store static files?
In the static
folder.
How do I access static files in templates?
Use the url_for()
function with the static
endpoint.
How do I handle user input in Flask?
Use request.args
or request.form
to access data from HTML forms.
How do I handle errors in Flask?
Use @app.errorhandler()
to define error handlers.
Should I use a virtual environment for Flask projects?
It’s highly recommended to isolate project dependencies.
How can I improve the performance of a Flask application?
Optimize database queries, use caching, and profile the application.
What are some common pitfalls when building Flask applications?
Security vulnerabilities, performance issues, and neglecting error handling.