Routes

The Basics

In all the examples above, any URL typed into the browser would render the same page. Usually, when we develop a web application, we want different URLs to load different pages. In other words, we want to define different request handlers to handle different URLs. In this part of the tutorial we will show how to do this using JustPy.

Please run the following program:

Setting a route with jp.Route

import justpy as jp

def hello_function1():
    wp = jp.WebPage()
    wp.add(jp.P(text='Hello there!', classes='text-5xl m-2'))
    return wp

jp.Route('/hello', hello_function1)

jp.justpy()#route_hello

Unless you go specifically to http://127.0.0.1:8000/hello you will get the 'Page not found' JustPy message. When a request arrives, JustPy checks if the route in the URL matches any of the defined routes. If it does, it runs the appropriate function and if not, it runs the function provided as the argument of justpy. If no argument is provided to justpy, the framework shows the 'Page not found' message.

Try running the following program:

Setting a route with jp.Route - default route + /hello

import justpy as jp

def hello_function2():
    wp = jp.WebPage()
    wp.add(jp.P(text='Hello there!', classes='text-5xl m-2'))
    return wp

def bye_function1():
    wp = jp.WebPage()
    wp.add(jp.P(text='Goodbye!', classes='text-5xl m-2'))
    return wp

jp.Route('/hello', hello_function2)

jp.justpy(bye_function1)#route_hello2

Type different URLs into the browser and see what happens. Unless the path is exactly '/hello', the bye_function will run and 'Goodbye!' will be displayed.

Warning

All paths must start with '/', otherwise an error occurs.

Using Decorators

It is common in Python web frameworks to use decorators to assign functions to routes because it is convenient and makes the code more readable. JustPy also supports assigning routes using decorators:

import justpy as jp

@jp.SetRoute('/hello')
def hello_function3():
    wp = jp.WebPage()
    wp.add(jp.P(text='Hello there!', classes='text-5xl m-2'))
    return wp

@jp.SetRoute('/bye')
def bye_function2():
    wp = jp.WebPage()
    wp.add(jp.P(text='Goodbye!', classes='text-5xl m-2'))
    return wp


jp.justpy()#route_hello3

The SetRoute decorator accepts as a parameter the route and assigns the decorated function to it. The program above defines two routes, '/hello' and '/bye'. URLs that do not include these exact routes, will cause the 'Page not found' message to appear.

Using Route Parameters

It is possible to use Starlette routing syntax to define routes with parameters. Parameters are exposed in the request.path.params dictionary:

import justpy as jp
def greeting_function(request):
    wp = jp.WebPage()
    wp.add(jp.P(text=f'Hello there, {request.path_params["name"]}!', classes='text-5xl m-2'))
    return wp
jp.Route('/hello/{name}', greeting_function)
jp.justpy()#route_hello4

For more examples using path and url parameters see request object.