Intermission: using Twisted to serve Django via wsgi

and now, while on break from our ongoing tutorial (table of contents).

are you tired of starting django and twisted via two separate processes, possibly having them run in two different shells for debugging purposes? i know i am.

fortunately, django and twisted can inter-operate – Django supports the Python wsgi interface, and twisted can be used to serve wsgi applications. this is actually the ideal method for having the two interact with each other (and is the first post in this tutorial that runs 100% counter to my disclaimer)

detailed documentation for this process is available at the twisted documentation site http://twistedmatrix.com/documents/current/web/howto/web-in-60/wsgi.html

give a shot to modifying your current tutorial code to make this work.


there are two components required to properly serve the django portions of this tutorial as wsgi resources:

  • configuring Django to work as twisted wsgi resource
  • serving the static components of django through twisted

this is slightly more complicated than it sounds, since, in newer versions, django dynamically searches through an ordered list of directories when serving its static components. using twisted to mimic that same functionality can take some work. i opted to use a custom directory scanning twisted resource

there aren’t very many decisions to make here; most of the work has to do with reading the documentation, and figuring out how to access the specific, relevant interfaces. if you’re stuck, you can find a clear example here; this basic resource might help, too.

 


tried it? given up? since i’ll be relying on this work when expanding the tutorial, it might be worth your time to see how i did it (and see if it makes sense to you). take a look at this commit/diff to get a list of the specific changes i made – let me know if it makes sense (or if i made a mistake/have a typo)


the git repository for the ongoing chat tutorial has this completed step tagged as v.0.2.1 – if you’ve already cloned the git repo, you can check out a clean version like so:

git checkout v0.2.1

detecting anagrams in python

Aside

what’s the shortest anagram detector you know how to write, in python?


this is one that keeps feeling like it should be a one liner (because it’s very similar to this one liner), but i suspect can’t be done in one line

highlight to see a solution.


def fn(x,y):
    if len(x) != len(y):
        return False
    for i in x:
        y = y.replace(i,'',1)
    return not len(y) > 0

PS: there’s a cool method for solving this for a fixed alphabet, using primes


[More programming riddles]

whyfore chat, with django, twisted and websockets?

Aside

upon seeing the work i’ve put into writing tutorials, showing how to get realtime chat working in django + twisted/websockets, you might make the assumption that i consider this architecture to be, in general, a good idea.

A.

twisted’s implementation of websockets is, as of this writing, not integrated into the main branch.

don’t use code that isn’t considered, by its authors, to be reliable enough to merge into and release as part of their application distribution.

B.

twisted is an event-driven networking engine
django is a solid, easy to use web framework
websockets, a tcp based protocol, is usually implemented as a strange mix between the tcp and http protocols

it is, generally speaking, not a good idea to mix abstraction levels; adding event-driven components to your application by combining twisted and django is a bad architectural decision. I strongly suggest you consider using twisted.web instead of mixing django and twisted.

websockets are a strange mix of protocols, and can be difficult to work with unless you are very careful with your choice of libraries and application design, scope and implementation. at the time of this post, i would recommend against using websockets, in production, with the standard deployment of twisted. i strongly urge you to consider the following alternatives, in rough order of likelihood to work for you: