đź’» Quartz 4.0

Flask

2 min read

uni
Flask is a lightweight web framework for Python that allows you to build web applications quickly and with minimal code.

Created by Armin Ronacher in 2010, Flask is considered a “micro” framework because it doesn’t require particular tools or libraries, giving developers flexibility in their implementation choices.

Key features:

  • Minimal core with extensible architecture
  • Built-in development server and debugger
  • RESTful request dispatching
  • Support for secure cookies (client-side sessions)
  • Template engine (Jinja2)
  • Unit testing support
pip install Flask
from flask import Flask
 
app = Flask(__name__) # the __name__ parameter determines the root path of the pplication, which is used to find resources like templates and static files
 
# define a route
@app.route('/')
def hello_world():
	return 'Hello,World!'
	
# run the application
if __name__ == '__main__':
	app.run(debug=True)

Routing

Routing in Flask maps URLs to specific functions that handle requests:

@app.route('/')
def home():
	return 'Welcome to the homepage!'
 
@app.route('/about')
def about():
	return 'About this website'
 
# Dynamic routing with parameters
@app.route('/user/<username>')
def show_user_profile(username):
	return f'User: {username}'
 
# Specifying the parameter type
@app.route('/post/<int:post_id>')
def show_post(post_id):
	return f'Post: {post_id}'

HTTP methods

Flask routes can handle different HTTP methods:

  • GET: retrieve data (default)
  • POST: submit data
  • PUT: updated existing data
  • DELETE: remove data
  • more
@app.route('/login', methods=['GET', 'POST'])
def login():
	if request.method == 'POST':
		# Handle form submission
		username = request.form.get('username')
		password = request.form.get('password')
		# Process login logic
		return f'Logged in as {username}'
	else:
		# Display login form
		return render_template('login.html')

Template

Flask uses Jinja2 as its template engine:

from flask import Flask, render_template
 
app = Flask(__name__)
 
@app.route('/hello/<name>')
def hello(name):
	return render_template('hello.html', name=name)
 
<!DOCTYPE html>
<html>
<head>
	<title>Hello Page</title>
</head>
<body>
	<h1>Hello, {{ name }}!</h1>
	{% if name == 'admin' %}
		<p>Welcome, administrator!</p>
	{% else %}
		<p>Welcome, user!</p>
	{% endif %}
</body>
</html>

Graph View

Backlinks