Took me 2 evenings to solve this one and was really hard to get my head around. Suggest searching the web for "python function closure" as your next port of call.

I'm struggling with the format of the output too, even though I get the output values correct. I created two lists of the positions and the peaks, then combined them into a dictionary like this {'pos':positions, 'peaks':peaks}. I also tried iterating through both lists to create a value:pair of each pos:peak, so output was {3:7, 6:3}.