• Preconditions in general


First and foremost, thanks for this great way of learning to program. I am not exactly new to the matter, but I never got really far, because I got bored with dry 'baby steps'. From what I've seen so far, the missions here will keep me interested.

Now to my question. I've reviewed some solutions to missions I had already completed. Some of them explicitly checked against the preconditions some did not. I was under the impression, that I can rely on the preconditions to always be true, so I don't have to check them myself. Or does precondition mean, that I have to check them explicitly?

On a side note, mission "House password" has a rather cryptic precondition:

re.match("[a-zA-Z0-9]+", password)

Now, I myself don't have a problem understanding it, since I have some prior knowledge of regular expressions. But, since the mission is marked as "Elementary" and is only 3rd on the "Home" list, I think it might be better to be more elaborate. I mean isn't this geared towards total beginners as well?