Artful Code

I long ago switched my company’s web applications from Code Igniter to Django. The main reasons were Django’s more powerful database API and Python’s maintainability and scalability over PHP.

The only feature of Code Igniter that I really miss in Django is the ability to add a page without first registering the url, formulating a regular expression to describe the parameters and variations of the view function, and then creating the view and template.

For a production website, this is a better method than Code Igniter’s strategy of http://domain.com/class/method/arg/arg/…/, but CI’s is much easier during development. My urls may change half a dozen (or more) times in the course of the project, especially if marketing or advertising is involved.

Fortunately, there is an easy fix. A generic, introspective function and a carefully crafted pattern in urls.py can save the day. The url pattern is simple enough:

(r'^/path/to/app/root/(?P.+?)/(?:(?P.+?)/)?$', free_pattern)

Placing this at the end of your urlpatterns tuple will allow any undefined urls to go through this as a last-chance catch-all. It captures the view as first segment (after the application’s root path) as well as any other text afterward (leaving out leading and trailing slashes).

Here is the function:

def free_pattern(request, view, segments=""):
    segments = segments.split(r'/')
    try:
        view_fn = getattr(PATH_TO_APP, view)
    except AttributeError:
        raise Http404
    return view_fn(request, *segments)

The function is simple enough. It accepts the request, the view’s name, and the rest of the segments. The segments are split by the forward slash to turn them into a list.

If the view is found in the appropriate module (defined using PATH_TO_APP, which should point to whichever application we are talking about), it is run with *segments expanded as its arguments. If the view is not found, we raise an Http404 error.

This could easily be expanded to introspect the path to the application, but since Django supports a number of different layouts for applications and projects, that will most likely be very customized to your setup.

For example, I typically store my applications in an apps module, each with its own urls.py file that is included at the project level. That way, an update to an application does not require synchronizing changes across multiple projects.