The disadvantage of pointing the questioner to documentation, or answering the question at a high level (with no code), is that the questioner might keep coming back, asking question after question until every little step that requires intelligence above that of a stoned tadpole is answered. And a question like the original post tends to raise that suspicion -- it doesn't contain enough information to truly help the questioner understand what s/he is doing wrong, but coincidentally it does contain enough information to give a working solution to the problem. At the same time, there's still a very good chance that the questioner is not a slacker cheating on homework; s/he is just not all that good at asking questions.

Of course, by giving a working solution, you've just given the suspected leech exactly what s/he was looking for. Or did you? Most probably not -- any professor who received an obfuscated answer such as the one above is obviously going to know that it's not the student's original work.