The semesters back up in full swing again - teaching 2 undergrad classes in person - CS0 in Python and CS1 in C++ along with my teacher certification class - Ethics via Zoom. Grand total of about 125 students. An error came up in the CS0 class the other day that reminded me how tough it is not only to prepare students to deal with all the things that can go wrong when learning to program but even for a teacher to realize what's going on.

Here's the code. It looks pretty straightforward and should work to draw a square.

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import turtle

wn = turtle.Screen()

crush = turtle.Turtle()

crush.forward(100)
crush.left(90)
crush.forward(100)
crush.right(90)
crush.forward(100)
crush.right(90)
crush.forward(100)
crush.right(90)

wn.exitonclick()
wn.mainloop()

Problem is, it didn't. Now, algorithmicaly this is correct and in fact the actual code looks correct as well but the student couldn't get it to run.

Here's an actual screenshot that resulted in the error. Can you spot the problem?

I spotted it pretty quickly. Not because I'm any good at this but because I've seen the error before. It turns out the student had named their program file turtle.py and so when line 1 tried to import turtle we ended up with a circular reference. Instead of loading the turtle graphics module, it would try to load itself. Had the actual error message remained on the screen it would have said something about "circular reference" but that wouldn't help a student and truth be told it probably wouldn't help most CS teachers in diagnosing the problem. Now, the student wasn't faultless here - I had explicitly stated that they should name their program file t1.py but we all know how well students follow directions ;-).

This is just one example of the myriad issues that arise when teaching programming. One could try to minimize these issue by working in sandboxed environments but then when students leave class and the sandbox. The sandbox makes life easier for the teacher but it's really only kicking the can down to someone else.

I remember this being a big deal when codecademy wa the big thing around a decade ago. Everyone went to their site and "learned" how to program. So many of them realized after finishing the course that they couldn't do anything outside of the little codecademy programming window. This isn't to say that Codecadmey wasn't a good product or service but students learning about how to deal with platform and implementation issues is a real one.

This particular issue left some hints - the error mentioned the import and said that it was circular but there are plenty of weird errors like this - dealing with versions, file and module locations, build systems and even things like disk quotas and file permissions that can make learning to program much more of a minefield than it should be.

I don't have any real answer as to how and when these issues should be dealt with - how much we should shield our students at first and how we should expose them to real world issues but it's probably something teachers should be talking about more.