A sample flask app

application.py

from flask import Flask

# create your app
app = Flask(__name__)

# create application routes
@app.route("/hello")
def say_hello():
  return "Hello!"
  
@app.route("/hello/<name>")
def hello_name(name):
  return "Hello, " + user_name + "!" # this will break

# run the app
app.run()