app.py

from markupsafe import escape
from flask import Flask, abort

app = Flask(__name__)

@app.route('/')
def hello():
    return '<h1>Ciao, Mondo!</h1>'
    
@app.route('/about/')
def about():
    return '<h3>Questa è una applicazione python - flask.</h3>'

@app.route('/capitalize/<word>/')
def capitalize(word):
    return '<h1>{}</h1>'.format(escape(word.capitalize()))
    
@app.route('/add/<int:n1>/<int:n2>/')
def add(n1, n2):
    return '<h1>{}</h1>'.format(n1 + n2)
    
@app.route('/users/<int:user_id>/')
def greet_user(user_id):
    users = ['Bob', 'Jane', 'Adam']
    try:
        return '<h2>Hi {}</h2>'.format(users[user_id])
    except IndexError:
        abort(404)