Entries in category "Python"

Recently Armin Ronacher (whose blog you should be reading if you do anything at all involving Python and the web) has published a couple of good articles poking at the current state of WSGI, the standard interface for Python web applications. Some of his comments dovetail nicely into concerns I’ve been trying to put into words for a while now, so I’m glad he’s posting on the subject and providing some context.

In short, I’ve come to have some rather severe misgivings about WSGI — both as ...

When licenses attack

Jacob posted twenty questions about the GPL. Zed followed with an explanation of why he placed Lamson under the GPL. This has provoked some discussion around the internets, some of which I have read and some of which I’ve ignored.

Unfortunately, there’s a lot of noise drowning out useful discussion, much of it centered around alleging — directly or indirectly — that if you ask questions about how the GPL interacts with other licenses, you must be trying to “get around” the GPL, or take someone’s GPL code and ...

A fun little bug

About two months ago, I quietly wrote and released a little Django application which generates cross-domain policy files for Flash (if you’ve never encountered this aspect of Flash, here’s an introductory article on how it works). I’ve done a bit of hacking on it in my spare time, and I’m pretty happy with it as an example of a simple, tightly-focused application; sometime soon I hope to write a bit more about the development process behind it, because it provides a useful real-world guide to some ...

PyCon ORM panel liveblog

I’m sitting about five rows back in the ballroom at the Hyatt, waiting for the ORM panel to begin.

First question: brief history of your ORM

SQLALchemy: wanted to do a CMS, but never ended up writing it. Had idea for a modular library to talk to databases, different bits you could use or not use — connection pooling, SQL expressions, ORM — as ...

Slides

Why I like pip

So yesterday I explained some of the reasons why I don’t like setuptools. In essence, my objections boil down to one idea: application packaging and application development should be orthogonal concerns. The way setuptools works, however, seems to tend, inevitably, toward coupling them to each other. I gave one example — the way the default behavior of installing zipped packages (an ironic twist: the man who so eloquently explained how Python is not Java has spent so much time and effort trying to implement Java packaging conventions in Python) leads ...

On packaging

So currently there’s a bit of a to-do involving Debian’s Ruby packaging team and the Ruby “gem” system. This document does a good job of summarizing the issues from Debian’s perspective. And of course, the Ruby side of it is no less heated; an example is here.

A lot of this is the usual back-and-forth between (on the one side) application developers working in one particular language, who want to distribute their applications to the widest possible audience and so use an operating-system-agnostic but language-specific tool for ...

Let’s talk about Python 3.0

There’s an old joke, so old that I don’t even know for certain where it originated, that’s often used to explain why big corporations do things the way they do. It involves some monkeys, a cage, a banana and a fire hose.

You build a nice big room-sized cage, and in one end of it you put five monkeys. In the other end you put the banana. Then you stand by with the fire hose. Sooner or later one of the monkeys is going to go after ...

Another take on content negotiation

Today my co-worker Daniel posted a class which performs content negotiation for Django views, allowing you to write a single view which returns any of several types of responses (e.g., HTML, JSON, XML) according to the incoming HTTP Accept header. While it’s certainly cool, he notes a couple of issues with it (including the redundancy it introduces in URL configuration).

Holiday decorations

Writing custom management commands

The other night in the #django-dev IRC channel, Russ, Eric and I were talking about custom management commands for certain types of common but tedious tasks; Eric was discussing the possibility of a command for automatically generating a tests module in a Django application, since he’s our resident unit-testing freak, and I started toying with the idea of one to generate basic admin declarations for the models in an application.

So I sat down and spent a few minutes writing the code. I haven’t decided yet whether I ...

So you want a dynamic form

So I havent really been doing much writing lately. That’s mostly a consequence of the fact that:

Let’s talk about documentation

One of the most active threads on reddit’s programming section right now discusses things people look for when reviewing someone else’s code; the article being discussed treats this as a great interview question and points to things like algorithm choices and object-oriented design as good responses. While these are important considerations, I’ve found I tend to make snap judgments long before I get to that level of analysis, and they’re almost always based on one key factor: documentation.

Batteries sold separately

At first glance, Google’s App Engine looks like a great way to build the next big web application; you get access to a massively scalable infrastructure, you get access to a huge existing authentication system, you get baked-in stats, you get all sorts of cool goodies.

Oh, and you get Python, which is a great language for writing web applications, and I’d be remiss if I didn’t take some pleasure in Django being available out of the box.

Where to find me at PyCon

My flight arrived in Chicago a while ago, and despite an attempt by the hotel to screw it up, I’m currently sitting in my room enjoying a beer before bed. Here’s my plan for the next few days:

Managers versus class methods

In the triumphant return of “James answers questions from the django-users list”, today I’d like to take a few moments to talk something that’s recently become something of a hot topic, spawning not one but two threads, as well as a couple off-list email discussions: what, exactly, is appropriate to put into a method on a custom manager as opposed to, say, a class method, and when and how can you tell?

This is a somewhat tricky question to answer, since there’s a substantial grey area where ...

On “conceptual integrity”

The key point Mark touches on is good documentation: ensuring that people see and understand the overarching structure of the framework is, ultimately, the key to helping people understand how it can help them get their work done. In the case of Django there is an official “overview” document, but it’s really not as good as it could be; it’s ...

Making magic

In yesterday’s article I spent a fair amount of time talking about the word “magic”, specifically in the context of Clarke’s Third Law, which states that

A big part of what I was getting at was that a lot of things which seem to be explicable only by appealing to “magic” are really just cases of technology — sometimes extremely simple technology — being used in a complex way. Or, to borrow an excellent turn of phrase from Terry Pratchett, “ninety percent ...

Be careful with your URL patterns

Tonight in the Django IRC channel, someone stumbled across a seemingly-odd error when trying to use a generic view:

TypeError: object_list() got multiple values for keyword argument 'queryset'

The problem turned out to be the URL pattern which was routing to the generic view. Consider a simple example, as might be found in a weblog application:

from django.conf.urls.defaults import *
from weblog.models import Entry

info_dict = {
    'queryset': Entry.objects.all()
}

urlpatterns = ('',
    (r'^(index|weblog)/$', 'django.views.generic.list_detail.object_list', info_dict)
)

PyCon 2007: Web frameworks panel

(this was liveblogged during the panel, and the only later edits were to correct a couple of typos and add this notice — the content has not been changed)

Titus, the moderator, has welcomed everyone. No blood shed so far. Probably not taking audience questions.

Titus pauses: “The most interesting thing about Django is, it’s what Guido would do.”

PyCon 2007: the prelude

So, I’m in Dallas, eagerly awaiting the beginning of the non-tutorial bits of PyCon 2007; I got here around 4:15PM (after a lovely flight where I was inadvertently bumped to first-class), and already things are rocking; I just got back from dinner and drinks with some folks who are doing really cool stuff with and to Django. Already got some interesting ideas and things to continue fleshing out, and I’ve got another four days to spend here.

Python framework design

Lately I’ve found myself being baited into the same old debate over and over and over again, and I’m getting tired of making the same arguments each time. Usually it begins with someone lamenting how Django is anti-community or too inflexible or generally suffering from a raging case of NIH. From there it progresses into people proclaiming how TurboGears or (more often) Pylons is objectively “better” because of how they’re designed, and how it would be nice for Django to follow their lead.

Programming tips: learn optimization strategies

Recently I spent a little time talking about the tradeoffs between “concise” code and readable code in Python. Throughout that entry, I was using as an example a simple function which calculates numbers in the Fibonacci sequence; here’s one variation:

def fib(n):
    if n < 2:
        return n
    return fib(n-1) + fib(n-2)

The Fibonacci sequence is a classic example from introductory programming materials, because it teaches recursion, and recursion is an important core concept for productive programming. But it can also be useful for another educational ...

Python tips: don’t be too concise

There’s an inherent tendency programmers have to take a piece of code and reduce it to the shortest possible form. The holy grail is, of course, cutting something down to a single line of code while still providing the same functionality; reducing a particular piece of code to a “one-liner”, especially if the code is somewhat complex, is sometimes viewed as a measure of a programmer’s intelligence or talent or both, and is often used as a sort of game (see Perl Golf, for example — the cult of ...

Entries in category “Python”

Let’s talk about WSGI