Notebook

Ordering related objects in Django

noreply@blogger.com (James Wheare) — Wed, 28 Nov 2007 00:59:00 +0000

Django models have a meta option order_with_respect_to that allows you to order objects within the scope of a related ForeignKey object.

This option adds an _order column to the model's database table to keep track of this ordering.

That's all very well, but if you need to change the sequence order you may well feel at a loss. The official documentation makes no mention of this option beyond a basic explanation of its purpose, and editing your objects in the built in admin app reveals no user interface for changing the ordering either. [1]

I managed to uncover a Python interface by delving into Django's API internals [2]. An object with related models that order with respect to it is given two handy methods:

get_RELATED_order()
set_RELATED_order()

where RELATED is the lowercased model name of the ordered objects


class Entry(model.Model):
    # ... fields

class Comment(model.Model):
    entry = model.ForeignKey(Entry, related_name='comments')
    # ... more fields
    
    class Meta:
        order_with_respect_to = 'entry'

Given the above example models, you can retrieve the order of an entry's comments:


>>> entry = Entry.objects.latest()
>>> entry.get_comment_order()
[1, 2, 3, 4]

And change the ordering by passing a list of comment ids back in.


>>> entry.set_comment_order([2, 1, 4, 3])

N.B. Be sure to pass in the same ids returned by get_comment_order

Two other handy methods exist for the Comment objects, get_next_in_order and get_previous_in_order [3]


>>> comment = Comment.objects.get(pk=3)
>>> comment.get_next_in_order()
<Comment: 4>
>>> comment.get_previous_in_order()
<Comment: 2>

A very early ticket is still open to restore this functionality to the admin app, and recent activity suggests it may well reappear soon. See also this thread on the django-developers mailing list. back

Look particularly at the two helper functions method_set_order and method_get_order in django.db.models.base. back

Theoretically at least, there's still a bug in get_previous_in_order but it should be fixed soon. Update: Fixed by the queryset-refactor back

Barcelona 11/07 Photos

noreply@blogger.com (James Wheare) — Sat, 24 Nov 2007 12:02:00 +0000

Bus times back online

noreply@blogger.com (James Wheare) — Sun, 18 Mar 2007 21:41:00 +0000

LiveBus.org is currently the first hit for "mash up offline" on Google. Not a particularly delightful situation, but I'm happy to say that the DeadBus has risen!

I've moved the site to a sultry new virtual private server at RimuHosting and real time bus updates are flowing once more. You shouldn't notice a difference, but I've now got a lot more freedom to tweak performance behind the scenes, and future downtime of this sort should be rare.
Disclaimer: Rare, not impossible

Do let me know if you're seeing funny stuff, things may have become muddled in the move.

LiveBus.org down

noreply@blogger.com (James Wheare) — Wed, 14 Feb 2007 19:06:00 +0000

Due to some server configuration issues, I've had to take LiveBus down until further notice. I'll hopefully have the problems solved soon and will make another announcement as soon as the site returns.

Sorry for the annoyance.

Update: The site's back online

LiveBus.org launched

noreply@blogger.com (James Wheare) — Thu, 08 Feb 2007 01:42:00 +0000

As part of a demo at the inaugural Oxford Geek Night (Update: podcasts now online at that link - hooray for immortalised mumblings!) on Wednesday night, I finally gave in and launched the project I've been working on for the last many months.

LiveBus.org is a free service that lets you find bus stops and routes on a map and look up live arrival times. It currently covers most routes in Oxfordshire and Surrey, and will hopefully be expanded in the future.

More info on LiveBus is at the about page.

Comments/questions/suggestions welcomed and encouraged.

How to piss me off...

noreply@blogger.com (James Wheare) — Wed, 17 Jan 2007 23:06:00 +0000

Papyrus? Just say no.

Yes, I am a font nerd.

Pen to paper

noreply@blogger.com (James Wheare) — Mon, 27 Feb 2006 05:51:00 +0000

I hate technical drawing.

Sitting down at a drawing board with a T-square and scale ruler to draw precise plans, elevations and the like can be a real chore when you're used to living the cosy Moleskine and biro lifestyle. I'd much rather churn out wobbly sketches of spidery landscaping and funkily shaded walls than spend hours accurately measuring out windows and scratching away ink smudges before scrapping my work and starting again because I was out by half a metre.

Alas, this is a necessary evil of the course, even with the modern luxury of eager CAD monkeys slaving away in the dungeons of architectural practice. So here's what I've got to do:

Plan
Four elevations
Section
Isometric
Sectional perspective showing construction details
Model at 1:50 scale

When what I really want to be coming up with is more stuff like this:

Such is the life of a student these days...

Foamboard fabrication and Photoshop

noreply@blogger.com (James Wheare) — Tue, 21 Feb 2006 22:42:00 +0000

Well I'm back from an extended hiatus, suitably replenished and motivated to get on with larnin' me some buildin' designin' skillz.

We've started our first individual project now. The brief: to design a family house for an 'Ideal Home Exhibition.' Salient conditions:

20 x 20 plot
Maximum interior space: 200m²
Masonry construction (bricks/stone/concrete blocks)

It's liberating being responsible for the entire design process and I'm a lot more inspired this time around.

Here's my concept model:

And here's an unsolicited paintover Fred worked up in a couple of hours and sent back to me:

This really helped make my day. Such an awesome contribution and visualisation tool. Thanks Fred, you never cease to amaze.

Anyway, these status updates helped keep me on track last semester, so I'll try to keep things moving along here.

Oh and a warm welcome to all iamcal.com visitors!

Home stretch

noreply@blogger.com (James Wheare) — Tue, 29 Nov 2005 12:41:00 +0000

Phew, that's two projects out the way... For the next three weeks we'll be crunching numbers on a roof system. The brief is to design a covered market area to fit in the library car park of Bradford-on-Avon. A truly dismal site but this project has more of an engineering slant anyway.

As for the writer's studio, the last few weeks were dedicated to frantically finishing our model, churning out last minute drawings and collating the juiciest material in an A3 brochure. I'm pretty happy with the result and generally had a lot of fun on this project.

Here's the completed brochure for you to feast your eyes upon.

brochure.pdf (1.4MB)

The tedium of drafting

noreply@blogger.com (James Wheare) — Wed, 09 Nov 2005 23:09:00 +0000

While I appreciate it's a handy skill to have, and producing a really stunning drawing can be very satisfying, repeatedly drawing and redrawing the same scheme in the same plane is a bit of a pain.

I redrew the plan for our writer's studio earlier tonight (which admittedly wasn't too bad since it was mostly tracing) and took a little webcam movie of the process for kicks. Check it out:

Drafting a writer's studio in plan starring James Wheare. (917kb)

I stumbled upon a fantastic blog earlier today, written by a third year Graphic Design student at Bath Spa University, just down the road. Claire Mills is examining the state of Graphic Design education and laying out what she feels such an experience should involve. Readers are encouraged to contribute their thoughts on the site, which may well be incorporated into her final major project.

As an Architecture student, her thoughts and ideas apply just as much to me as to anyone pursuing a design education and I'd definitely recommend you give it a look.

While I'm here, I'd just like to point you in the direction of an incredibly talented artist I went to school with. Fred Stidston's paintings are breathtaking, vivid and teaming with character and you should all run to his site this instant!

Right, now for some two-point perspective love...

No Balustrades

noreply@blogger.com (James Wheare) — Fri, 04 Nov 2005 01:53:00 +0000

We started building a balsa wood model today after some tedious number crunching to sort out dimensions. Gotta work up some larger scale construction details to show all the exciting joint work we've planned. Hmm... yes well I hope this is more interesting:

More later perhaps.

Reaching skyward

noreply@blogger.com (James Wheare) — Sun, 30 Oct 2005 23:29:00 +0000

Determining heights and proportions from scratch with no scaled reference is a bit of a pain, but eminently doable.

Yes, I'm aware of the unintelligible nature of this cross-section and the distinct lack of a roof. Take it as an opportunity to stretch your imaginative flair.

Ruby's been visiting from Wimbledon for the weekend on retreat from designing costumes. That's a working retreat... of course. In the main, this work has involved languishing in bed calling out eccentricities such as "If you were a Norse God, who would you be?" and generally being a lady of consummate splendour.

What a muse.

As promised

noreply@blogger.com (James Wheare) — Sat, 29 Oct 2005 21:33:00 +0000

So, here's what I spent three hours doing today.

Three hours?! Yeah, scale drawing is a bitch. As should be obvious from this plan, the scheme involves a contemporary reinterpretation of the traditional Japanese Machiya construction style for use as a writer's studio.

Yes... quite.

So er... while I'm down here, I'd like to shout out to my homey Hugh, who's serving up some compsci magic at Cambridge. Word up in your shizzle, dog.

Webcam

noreply@blogger.com (James Wheare) — Fri, 28 Oct 2005 00:36:00 +0000

As you can probably see, I've got my webcam set up in the sidebar over there. Now you can keep an eye on me procrastinating or if you're lucky, draughting some architectural masterpiece.

Speaking of which, I've now started project 2, a timber framed writer's studio. I'll have some drawings to share with you tomorrow but until then, here's a teaser.

Well, at least, I hope that turns out to be an accurate teaser.

Fare thee well, o ye wonders of the modern world.

Dilatory inauguration

noreply@blogger.com (James Wheare) — Thu, 27 Oct 2005 02:11:00 +0000

Well here we have it, I'm blogging (again) and I still hate that word. I'm not sure what sort of goodness will be cropping up here but I expect it'll be along the lines of thoughts, commentary, imagery and criticism. You know, the usual.

Righto, just because text is boring (?), here's a sample of what I've been up to these past few weeks: