Parts of a Flask Web App

@app.route

This defines where a particular path in the url relates too:

@app.route("/")
def hello():
    return "Hello World!"

When the app server is running, visiting the root will produce the message 'Hello World!'. The code below will also display this if you visit '/home' on the app server:

@app.route("/")
@app.route("/home")
def hello():
    return "Hello World!"

Parameters

The example below will just display the message:

@app.route("/")
def hello():
    return "Hello World!"

You can also use parameters:

@app.route("/<name>")
def hello(name):
    return "Hello "+name

Using this method the parameters are passed as strings, and you may need to convert them. In this example the URL '/Wayne' will display the message 'Hello Wayne'.

url_for

If you look at this example:

@app.route("/home")
def home():
    return "test"
 
@app.route("/hello")
def hello():
    return "Hello World!"

it creates 2 paths, one for '/hello' (runs 'def hello()') and one for '/home' (runs 'def home()'). url_for will accept the name of the method (ie def ....) and return the route.

so:

url_for('hello')

will return:

/hello