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Nov 11 2012

edX 6.00x week 6 – going up a gear

Whew. Suddenly, after five relatively straightforward weeks, 6.00x has kicked up into a higher gear. I’ve just got to the end of this week’s lectures, finger exercises and problem set and it’s been far more taxing than anything, including the midterm exam, that preceded it. The main theme of the week has been an introduction to object-oriented programming, with various concepts (exceptions, classes, instances, inheritance and so on) being used for the first time.

This is the part of the course, while not being totally new to me, is the part that I’m least familiar with. All of the ‘production’ code that I ever cut in my career was definitely not object-oriented – and what little OO code I have created has been for the purposes of demonstrating other software packages, rather than being something coded to form an integral part of such a package. There’s a difference – as if your code doesn’t need to go into production you start to get a little sloppy about things – and the edX grader definitely won’t let you get away with that!

This week’s problem set has involved writing a number of classes to complete a program which selects and displays content from rss feeds if particular trigger words or combinations of them appear in its configuration file. There was definitely some subtlety required to complete the task successfully and the very final part of it took me ages because I’d made a silly error. However, I appeared to be in good company, as at least two other people on the edX forum had made exactly the same error. (Hint: if you end up with the error message: ‘str’ object has no attribute ‘evaluate’, for the final part of problem set 6, have a look at what you’re passing to the boolean triggers. It should be the actual object from the triggerMap dictionary, not its constructor).

At the time of writing (Sunday afternoon), neither of the graders for the penultimate and final part of problem set 6 are up and running, which is a little frustrating. Adding to the frustration this week has also been the bug in the problem set that becomes apparent when doing filtering (the code is expecting methods like get_guid() instead of getGuid() as was required by the grader earlier on) – but this is simple to fix of course.

There was also a documentation issue in one of the earlier finger exercises. In it, the grader tests whether your isPrime() function can handle an input value of 0, whereas the problem definition says that the function only needs to consider numbers greater than or equal to 1. Fortunately, the diagnostic output from the grader is very useful in ironing out such wrinkles. Being able to debug other people’s code and documentation is an important skill for any programmer to pick up!

However these minor problems, grader outages, the availability of only the current week’s material and the push back of the release date for each week’s material from Mondays to Wednesdays all give an impression that the 6.00x course team are a little overstretched – much more so than was apparent on 6.002x earlier on this year. I don’t think anyone on the course this time around minds being a guinea pig (after all, the content is excellent and it’s free to participate), but it’s clearly something that will need addressing in future if the plan to charge for completion certificates is to come to fruition.

After all, one of the benefits of online or distance education should be that the material is available for you to work on when you have the time to study it. Getting ahead of the timetable was something I always tried to do on my OU courses, as you never know when real life is going to get in the way. And for me, I think real life is just about to do exactly that. But for the moment, I’m just waiting impatiently for week 7 to start.

Update 12th November

The graders for the final two parts of problem set 6 are now up and running. But guess what. Despite the docstring for makeTrigger() being explicit that it returns a value of None, it won’t pass the grader unless you return triggerMap[name]. Sighs again.

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