A few years ago nearly all the code I wrote was in C++, but increasingly I’m finding myself writing in a variety of mostly C-style languages and having to perform crunching mental gear changes as I switch between them.

In the interests of making these language switches less painful I thought about listing the commonly used features of the languages I commonly use in a side-by-side format. Luckily I’m a lazy programmer, the web is large and there’s nothing new under the sun, so I quickly found Hyperpolyglot which provides commonly used programming language features in a side-by-side format, which is what I wanted. Nearly.

Hyperpolyglot organizes it’s language comparisons in to several catagories: scripting languages, C++ family languages, embeddable languages and so on. In my case (and I suspect in many cases) the languages I wanted to compare were spread across several pages.

After briefly considering some cut and paste to get what I wanted I started playing with Google Spreadsheets, which has a very nifty importHtml function which allowed me to pull the Hyperpolyglot data in to several sheets which can be combined to produce arbitrary language comparisons.

It’s not perfect as different languages have different features and in some cases the Hyperpolyglot data doesn’t use exactly the same terms across tables (“version used” vs “versions used”) and I’m not a spreadsheet ninja, but it’s good enough to generate PDFs like this JavaScript Python Java C++ Comparision. As a Hyperpolyglot derivative work, The Super Hyperpolyglot Spreadsheet is licensed under the Creative Commons Attribution-ShareAlike 3.0 License, please let me know if you improve it.

Over the last couple of years I’ve found myself using python decorators to annotate handlers for web requests more and more, both when using Django and with micro-frameworks like mnml and newf.

Where the same functionality is required for all handlers, or the required functionality can be determined from standard request or response headers, using WSGI or Django middleware is fine, but where the required functionality is varies based on the handler its much cleaner to use a parameterised decorator than poluting the environment or response objects just to control the middleware. Functionality can be added to a framework as a suite of decorators and plugged together in an aspect oriented way like lego to easily build up sophisticated behaviours.

Unlike other mechanisms for implementing macros, templating or aspect orientation that introduce a new language, python decorators are pure syntactic sugar that under the hood are simply rewritten as python expressions:

@requires_oauth_scope("email")
def notify_friends(request):
    pass

Is simply shorthand for:

def notify_friends(request):
    pass

notify_friends = requires_oauth_scope("email")(notify_friends)

This simplicity is powerful as it allows decorators to also be used as normal functions, for example to build up higher level decorators that bundle common decorator configurations, but it also means that decorators potentially interact badly with another powerful Python feature: introspection.

In the above example the undecorated notify_friends function has the __name__ “notify_friends”, but the decorated function has the __name__ “requires_oauth_scope”. When decorators are used extensively, this can seriously impact the usefulness of introspection for debugging or generating documentation.

Decorating your decorators with the functools @wraps decorator, which copies the __name__ of the wrapped function over to the wrapping function solves this introspection problem, but introduces another: the decorators now become invisible to introspection. In the example above the __name__ of the decorated function would now be “notify_friends” as in the undecorated case, but we wouldn’t know that the function had been decorated or not.

A potential solution to this new problem is to store the details about the decoration in another attribute that can be inspected at runtime. In addition to copying over the __name__ attribute, functools.wraps also copies over the target __dict__ by default, allowing it to be used to store information about the decoration and be correctly copied over when decorators are chained:

from functools import wraps

def requires_oauth_scope(scope):

    def decorator(target):

        target.__dict__["my_project_requires_oauth_scope"] = scope

        @wraps(target)
        def wrapper(*args, **kwargs):
            # return target(*args, **kwargs) or FORBIDDEN if token does not have required scope

        return wrapper
    return decorator

By constructing decorators in this way we get the benefits of python decorators and more declarative C# style attributes that are visible to introspection.

Jamie has just uploaded the movie of my talk “The Why and How of Automated Testing with Python and Django” which I gave at BrightonPy a week ago (and this time it really is a movie, clocking in at a feature length 1 hr and 35 minutes). The audio on the video is fine (and arguably the laptop-eye-view video is improved by chopping my head off for large parts of the talk), but it’s tricky to see the slides on the video, so I’ve uploaded them to slideshare.

The talk rambles a bit in places and there are a couple of things that betray my static language roots for example you can’t actually use unit tests to discover dependencies as easily in python as you can in C++. I’m also already evolving the JS testing stack I talk about here: moving from qunit, qmock and Selenium to jsmockito and possibly JsTestDriver. Overall I think it’s a pretty good overview of how an agile software engineering process can be screwed together.

Many thanks to @garethr for donating his Fabric scripts, Spike for his database migration cameo, Si for recommending Hudson, Dave for hooking me on automated testing and j4mie for organising the night and wrangling the video. If you’d like me to help your organisation improve its agile engineering process, please get in touch.

Since leaving Linden Lab I have been talking to a number of people about doing freelance consulting and development work while I get my start-up off the ground and last week got round to setting up a UK limited company so that people will actually be able to pay me.

Setting up a company is insanely easy these days: if you go to companies made simple it will cost you less than £17 and 10 minutes of form filling. Coming up with a name is harder, but within a couple of hours I found that 18dex was available as a .com TLD, twitter account and facebook username. Meaningful 5 character .coms are pretty tricky to come by these days, so I snapped it up and 18 Dexterity Ltd. was born — a pretty fantastically geeky name for an agile software engineering company I hope you’ll agree.

A few minutes later I had a holding page up for 18dex.com, but it looked pretty sad with no content, so I started thinking about setting it up as a blog. I have a stack of relevant software engineering posts on jimpurbrick.com from the last few years, but they are sandwiched between less relevant posts on 100robots, Second Life and various miscellany. I didn’t want to move the software engineering posts from jimpurbrick.com as they’re part of what I do and regularly updating a single blog is quite enough work. I also didn’t want to copy the posts from one blog to another as it would potentially end up with 2 independent comment threads on each blog. There would be no definitive version of a post, a blatant violation of Don’t Repeat Yourself.

Luckily Django includes a piece of machinery to deal with this problem in its sites framework, something I’ve been meaning to have a closer look at for some time. The sites machinery simply lets you associate a piece of content with a site and keeps track of the current site, allowing you to filter the content in the database to only show a subset on each site.

While the byteflow blog engine I use for jimpurbrick.com supports the sites framework, each post is associated with a single site via a ForeignKey. In order to allow posts to be shown on both jimpurbrick.com and 18dex.com I had to change that ForeignKey field to be a ManyToManyField: a single line change in the python code, but something that requires a little wrangling to massage the existing data to fit the new model.

I’ve been using the excellent South in all my recent projects to allow me to easily migrate data across django model changes. Although jimpurbrick.com dates from long before South was available I managed to convince south to manage the migration by dumping the blog_post table to json, dropping the table and recreating it with south, reloading the data and then letting south migrate the data to the new ManyToMany schema. While this was slightly more fiddly than it could have been it means that the blog app is now being managed by south, which will make future development on the blogs much easier.

Once I had migrated the data to the new model and associated the software engineering posts in jimpurbrick.com with both sites in the django admin interface all that remained was for me to clone the jimpurbrick.com directory with mercurial to create an 18dex.com directory and choose and tweak a byteflow theme for the new site.

Once again I’ve been very impressed with Django and Byteflow, which have proven to be incredibly powerful tools that are very easy to work with. In a few hours I was able to create professional and personal views on to my blogging which can be easily administered from a single interface and allow comment threads and users to easily flow between them. If you’re just interested in my software engineering posts, head over to 18dex.com, if you want to hear about music, Second Life and everything else I get up to, stay subscribed to jimpurbrick.com. If you notice anything broken on either blog, then please leave a comment to let me know.

Incredibly, 100 robots have 4 gigs lined up in the next 3 weeks: tomorrow we’re playing at an electro/rock night at The Freebutt with Bang Bang Eche, Son of Robot and labasheeda, then next Thursday we’re playing at a more hip hop themed night at The Hope with Tactical Thinking and L-Mo. On the 2nd of December we’re playing at the music hack themed £5 App Christmas Special, where I’ll also be giving a talk about my open source guitar mounted iPhone multitouch Mrmr/LiveAPI/OSC wireless Ableton Live interface and then using it to play live. Finally on the 11th of December we’re playing at the Linden Lab Brighton Christmas party along with the other real rock band that formed from the remnants of the all conquering Linden Lab Brighton virtual Rock Band.

Whew. It’s going to be a busy few weeks. If you can come to any of the gigs, please do. It’s going to be fun: we’ll be playing brand new songs including our first excursion in to Rock/Dubstep and trying out new ways of performing. If all the gigs weren’t in Brighton I’d call it a tour…