TurnKey Linux Virtual Appliance Library

Python property gotcha

If you like using a single getter/setter function for your properties, watch out if using None for the default. If you do that you won't be able to set your property to None!

Example code and workaround...

Use the stash, Luke (git-stash)

I was in the middle of developing a new feature for the TurnKey Hub when I received a bug report that needed to be fixed.

What to do? Throw away my current changes? Checkout a clean branch? Of course not! Just stash my changes away, fix the bug, and get my changes back so I can continue development.

Amazon FPS (flexible payments system) in a nutshell

A few weeks ago I looked into Amazon FPS (Flexible Payments Service), just to see what our options are for premium services like commercial support. You know, the stuff we can't give away even if we wanted to because their are real costs involved which we couldn't subsidize without going bankrupt.

Note that we're probably not going to be using FPS in the near term but I did research it exhaustively before I ruled it out (for now). While it's fresh in my mind here's the summary for the benefit of those who might be considering it as an option.

My code refactoring algorithm

You're looking at a block of Python code. It's not immediately obvious what it does. It's sort of a mess and you realize it needs to be refactored. But how? What mental algorithm do you use?

Neat trick: invoking a Python debugger at an arbitrary point in your program

Do you find yourself occasionally wishing you could freeze a misbehaving program at an arbitrary point in time and then examining what was going on interactively?

That's exactly what the debugger is for, but sometimes it's just too much of a bother to run your program inside it, you have to set breakpoints, etc.

Well there's a really simple alternative: call the debugger from an arbitrary point in your program, like this...

Growl type notifications in Django

First, a little background

Django has an excellent messages framework which provides support for cookie and session-based messaging, for both anonymous and authenticated users.

The messages framework allows you to temporarily store messages in one request, and retrieve them for display in a subsequent request (usually the next one). Every message is tagged with a specific level determining its priority (e.g. success, info, error).

Prevent double click on form submission

Recently I've been going over the Hub logs and fixing issues which have caused exceptions to be raised in the application.

One in particular had me stumped for a while. An exception was being raised in an attempt to unregister a server from the Hub, but the server did not exist in the database - in theory this is impossible and should never happen.

A lazy yet surprisingly effective approach to regression testing

To regression test, or not to regression test

Building up a proper testing suite can involve a good amount of work, which I'd prefer to avoid because it's boring and I'm lazy.

On the other hand, if I'm not careful, taking shortcuts that save effort in the short run could lead to a massive productivity hit further down the road.

For example, let's say instead of building up a rigorous test suite I test my code manually, and give a lot of careful thought to its correctness.

Right now I think I'm OK. But how long will it stay that way?

Python performance tests reaffirms "premature optimization is the root of all evil"

"Premature optimization is the root of all evil"

Today while programming I found myself thinking about the performance impact of various basic Python operations such as method invocation, the "in" operator, etc.

This is a mistake because you really shouldn't be thinking about this stuff while programming. The performance impact of doing things one way vs another way is usually so small that you couldn't measure it.

Practical guidelines for beautiful Python code

Every now and then Liraz and I find ourselves chatting about how much we love Python, but more so the lessons we have learned from coding, and how to apply them to create beautiful Python code. I've tried to refine some of the "lessons" into practical guidelines that I apply religiously to all new code I write, and the refactoring of old code I written.