I'd just picked up python and was having so much fun going through the project Euler problems.
I can't remember which question it was for but we had to know the length of an integer. At that point I hadn't learnt about type conversion so had to implement it the way the author wants his students to do it.
I remember fondly as well that I hadn't learnt about the modulo operator and had to implement that by myself as well.
I couldn't believe it when I got the answer and progressed to the forum where others shared their answers and they were doing it on one line with %!
Good times!