Posts tagged ‘Ruby’

This is the second time I’ve attended Nordic Ruby, you can read about what I thought last year here. This year I enjoyed the conference more, for several reasons. There were some small changes in the way it was organized, (on a Friday and Saturday instead of taking up a whole weekend), a better choice of speakers and topics, (less technical, more inspirational), and I knew more of the people there.

One of the themes of the conference was diversity, which I was very, very happy to see. There was an inspiring talk by Joshua Wehner about this topic, taking up some depressing statistics about the IT industry in general and open source software in particular. What struck me most was that he said the statistics for women involvement are improving in many formerly male-dominated disciplines, like maths, physics and law, but in computing, the situation was actually better 20 years ago than it is now. The curves are pointing the wrong way in our industry.

Having said that, there were slightly more women at the conference this year than last, I think I counted 4 of 150, compared with 2 of 90 last year. There were also far fewer references to science fiction movies from the speakers this year 😉

Joshua did take up several things that we could do practically to reduce bias and positively encourage diversity. He’s written about some of them in this blog post. Another one he mentioned that I liked was the “no asshole rule”. If people engage in arrogant one-upmanship, talk down to others, and emphasize their superior programming abilities, they should be regarded as not just annoying, but actually incompetent. Developing software is a multi-faceted skill, and it takes a lot more than just writing good code to be a good software developer.

Joe O’Brien continued the diversity theme in his talk “Taking back education” by basically arguing that having a degree in computer science correlates very badly with being a good software developer, and that we should be finding ways to bring people into our industry who have non-traditional backgrounds. He advocated companies to start apprenticeship programmes, while conceding that this model of education doesn’t scale very well. He talked about getting a group of companies together to set up a “code school”. He said “forget universities when it comes to education [of software developers]. We’re better at it”

I applaud his efforts to bring a more diverse range of people into the industry, and I think my recent experiences teaching a group like this are relevant. I think I’ll write a separate blog post about that experience, but basically I think the idea of a “code school” is a good one, and similar institutions probably already exist, and could add a course in software development to their programme of courses in practical skills. For this to happen it’s up to companies to put in time and energy setting them up, rather than just complaining that when they put out a job advert, all they get are white male applicants between the ages of 25-35, so it’s not their fault.

Another talk that deserves a mention is the one by Joseph Wilk. He spoke about “The Limited Red Society” which is an idea that Joshua Kerievsky came up with. I heard Joshua speak about it at XP2009, and I thought Joseph did a very good job of explaining what it is, and why it’s important.

Basically the idea is that although you need your tests to go red during TDD, if they stay red for any length of time, it can get you into trouble. While they are red, you can’t check in, ship your code, or change to working on a different task. This is one motivation for trying to measure, and limit, how much of the time your tests are red. It’s also about more generally improving the feedback we get for ourselves while we work. Professional sports stars spend time analysing and visualizing their performances (where balls land on a tennis court, footballers rates of passing etc). We programmers could benefit from that kind of thing too.

Joseph has invented a tool that helps him to track his state when doing TDD. It’s a simple monitoring program that makes a note every time he runs his tests. It’s not as elaborate as the commercial tool offered by Joshua Kerievsky’s company, but it does work with Ruby and Cucumber. Joseph also has his tool connected to his CI server so that it runs tests that have failed recently in his and others’ checkouts first in the CI test run. He also gathers statistics about individual tests, how often they fail, and whether they are fixed without the production code needing to be changed – a way of spotting fragile tests.

I think this kind of statistics gathering is really interesting and I think Joseph will just have more insights to share as he gathers more data and does more analysis. I’ve been experimenting with the tool provided by for measuring my performance at code katas, but Joseph seems to be taking this all to the next level.

Overall I thoroughly enjoyed Nordic Ruby. (I still think it would be improved by some actual open space sessions though). I talked to loads of really interesting people, enjoyed good food and drink in comfortable surroundings, and listened to some people give excellent talks. Thanks for organizing a great conference, Elabs.

Last night at GothPy we had a play with Django, a web application framework for Python. I’m fairly familiar with Rails, so it was interesting to see a different take on solving the same kinds of problems.

I downloaded Django for the first time when preparing for the meeting, and spent about a day going through the tutorial and trying stuff out. At the meeting were a few people who have used Django before, notably Mikko Hellsing, who has worked with it daily for several years.

It was so much easier learning the tool from people who knew it than by reading the documentation. Constant code review and real time answering of questions is just brilliant for learning.

At the meeting we decided to implement a very very simple web application, similar to the one that Johannes Brodwall performed as a Kata at XP2010 together with Ivar Nilsen. He calls it “Java EE Spike Kata” since he does it in Java with no particular web frameworks, just what comes with Java. (There is a video of him doing it on his blog, and sample solution here on github).

I thought we should be able to implement the same little application in any web framework, and it might be interesting to see differences, so I though we should try doing it in Django. It just involves two pages. One page “Add User” which lets you create a new user and save it to the database, and another page “Search User” which lets you search for users, and presents results. So the scenario is to create a user, search for them, and see they are returned.

When I work on a problem in Rails I usually start with a Cucumber scenario for the feature, and I discovered there is a python version of Cucumber called Lettuce. We could have course have just used Cucumber with python, but given the big “WARNING – Experimental” notice Aslak wrote on this page, I thought we could give Lettuce a try.

So at the meeting we all worked together with one laptop and a projector, (me at the keyboard), and we started with a Lettuce scenario. We implemented step definitions using Django’s test Client, which is a kind of headless browser that understands how to instrument a Django application. Then we spent a couple of hours writing Django code together until the scenario was all green.

The code we ended up with isn’t much to write home about, but I’ve put it up on github here.

What we learned from this exercise
Of course since I know Rails much better, I found it interesting to compare the two web frameworks. Django seems similar in many ways. It was dead easy to get up and running, it gives you a basic structure for your code, and separates the model from the presentation layer.

The O-R mapping looks quite similar to ActiveRecord in the way you declare model classes backed by tables in the db. The presentation layer seems to have a different philosophy from Rails though. The html view part is rather loosely coupled to your application, and doesn’t allow you to embed real python code in it, just basic control structures.

You hook up the html to the controller code using url regular expression matching. I was a little confused about exactly how was supposed to work, since what I considered controller code was put in a file called “”. Most of the code we wrote ended up in here, and I feel a bit unhappy with it. It seems to be a mixture of stuff at all levels of abstraction. The Django Form objects we used seemed quite powerful though, and reduced the amount of code we had to write.

The biggest difference I noticed compared with Rails was how explicit Python is about where stuff comes from. You always have to declaratively import or pass stuff before you can use it, so I found it straightforward to follow the connections and work out which code was executed and where it came from. I think that is because of Python’s philosophy of strict namespaces, which Ruby doesn’t have so much of.

I also liked the way Django encourages you to structure a larger web application into a lot of independent smaller ones, and lets you include and re-use other people’s small apps. Rails has plugins too of course, but I thought Django’s way made it seem very natural to contribute and re-use code.

Comparing Lettuce to Cucumber, they look almost the same, (by design). One small difference I found was that Cucumber step definitions don’t care if you write “Given”, “When” or “Then” in front of them, whereas Lettuce did. So I had steps like this:

Then I should see "results found"
And I should see "Name"

where the first step passed and the second step was reported as unimplemented by Lettuce. So Lettuce need a little more work to be really usable.

I was also pretty disappointed by the Django test client for implementing test steps. It seemed to interact with pages at an abstraction layer lower than I am used to – at the level of making post and get requests and parsing html as a dom. I missed Capybara and its DSL for interacting with web pages. I couldn’t find any equivalent. I probably should have turned to Selenium directly, but since we had no client side javascript it seemed overkill. (Francisco Souza has written about using Lettuce with Selenium compared with the Django test client here).

When it comes to unit-level testing, Django provides an extension to the normal unittest tool that comes with python (unittest was originally based on JUnit). We didn’t do much with it at the session, and it seemed to work fine. It’s nothing like RSpec though, and I miss that expressiveness and structure for my tests whenever I work in Python.

All in all it was fun to look at Django with a group and to get some really helpful comments and insights from people who know it far better than I do. The Kata we chose seemed to work ok, but I should really do it again in Rails since I spent the whole time comparing Django with Rails in my head, not Django with Johannes’ Java code 🙂

My conclusions are basically that Django looks like a good alternative to Rails. It would take time to learn, and surely has strengths and weaknesses I can’t really evaluate from one short session looking at it. However, I’d fairly sure I’d have to do some work improving the testing tools if I was going to be happy working with it for real.

I was at the local Ruby User Group last night, and I coded up KataMontyHall (see below) as a prepared Kata in front of the group. I got some great comments and feedback while I was coding, and I think the solution I ended up with was better than any I had created by myself during my practice sessions. I also got some new ideas about different approaches which I plan to try out and see if they improve the code even more.

Dave Hoover was visiting from the US, on his way to a speaking engagement at Öredev. He and I were both surprised to discover a common interest in the Monty Hall Dilemma. Dave has previously worked on it, and he showed us some code that he wrote 5 or 6 years ago when he was still learning Ruby. He even wrote an online version of the game when he was first learning ajax, that you can play yourself!

The Monty Hall Dilemma
There is a gameshow hosted by Monty Hall where contestants try to win a big prize, which is behind one of three doors. The contestant begins by choosing a door, but not opening it. Then Monty steps forward and opens one of the other doors. He reveals a goat (!). Then the contestant has the choice of either sticking with the door they have already chosen, or switching to the other unopened door. Whichever door the contestant decides on will be opened, and if they find the prize, they get to keep it. (I’m not sure what happens if they get the second goat!) So what’s the best strategy? Stick or switch?

People are biased towards sticking with what they’ve chosen, and the vast majority of people stick with the door they choose originally. Intuitively there should be an equal chance of the prize being behind any of the three doors, so it shouldn’t matter if you stick or switch. However, in this case, your intuition is wrong. You are twice as likely to win the prize if you switch to the other unopened door.

I am not the only one to think this result is incorrect, apparently famous mathematicians have also refused to accept it. What finally convinced them, was a computer simulation. Hmm I thought, that sounds like an interesting piece of code 🙂

Pigeons are smarter than Humans
I heard about the Monty Hall Dilemma listening to the quirks and quarks podcast. Apparently humans are strange, because they don’t learn to switch doors. Some researchers set up the same problem for pigeons, with birdseed behind one of the doors, and found the birds quickly learnt to switch doors. You can read the research for yourself!

So if you, like me, are keen to prove yourself more intelligent than a pigeon, why don’t you spend some time writing a little program that simulates the game? If you get it right, your version of KataMontyHall should clearly show that switching doors is the best strategy 🙂