Duende web framework

What is it ?

Duende is a WSGI web framework built on top of Paster. It uses SQLAlchemy as ORM and Jinja2 for templates.

The main difference with other frameworks is that duende don't use URL to controller routes as most of python web frameworks do, but instead it uses a fixed URL dispatching system.

By using a fixed system is not necessary to maintain URL mapping file(s) for each controller or to inspect files looking for exposed controller instances or functions. But drawback of using a fixed system is that you loose some flexibility.

Installation and setup

To install duende just run:

pip install duende

or:

easy_install duende

After you can start a new application named foo by running:

paster create -t duende foo

You can replace foo for the name of your application, but have in mind that examples will use foo as application name.

This command is going to create directory with a duende application skeleton that you can use as a start base.

Inside the new directory you will need to create some folders that are used by default settings to keep session and template cache. These folders are var/sessions/data, var/sessions/lock and var/templates/cache.

Settings are stored in a file called duende.ini (you can change the name if you want). Edit this file to setup values for your specific needs.

After you finish changing settings run:

paster serve duende.ini

and open http://localhost:8080/ in your browser. You will see a "404 Not Found" message because there is no view handler to manage the request yet :).

First steps

New create a src/foo/view/root.py file so it looks like:

# -*- coding: utf8 -*-
from duende.lib.view import utf8_text
from duende.lib.view import redirect
from duende.lib.view import restrict

from foo import url


@redirect
def index(request):
    #redirect to /login URL
    return url('/login/')


@restrict('GET')
@utf8_text
def login(request):
    #handle /login requests by printing a text
    return u'Wops ! its just a test'

Save it and open http://localhost:8080/ in your browser. This time you will be redirected to http://localhost:8080/login/ where a text will be displayed.

Inside your application directory there is a second ini file called urls.ini. This file "plug" different applications to a base URL, allowing Duende to know wich application will handle each request.

By default when you access an application base URL like / (for default app), or /blog/ for an application "plugged" in /blog, Duende will look for a file called root.py inside that application view directory, and then for a function called index. In similar way it will inspect URLs to see mapped application, and then look inside view directory for a module and a function to handle request. For example, in case of http://localhost:8080/user/login/ the steps to get handler will be:

• If there is an app plugged to /user use that app function view.root.login() to generate response
• Else get app plugged to / URL and use its view.user.login() to generate response