Choosing Python Data Structures, for Kids

By this point a child knows lists and dictionaries as separate tools, but has rarely been asked to choose between them for the SAME piece of information. This topic opens by storing one small roster of characters four different ways — two parallel lists, a list of dictionaries, a dictionary of lists — so the tradeoffs are something a learner can observe directly rather than take on faith: which shape makes 'process everyone one at a time' natural, and which makes 'grab one field from everyone at once' natural.

Nested access follows as its own real skill, not an extension of something already covered: reading a value two levels deep, looping over nested data with a loop inside a loop, and updating a value that lives inside a dictionary that lives inside a list — a genuinely different move from updating a flat variable, even though it looks similar at a glance.

The topic closes with sets, introduced for the one job they do better than any other structure: removing duplicates and checking membership quickly. It states their real limitation directly rather than working around it quietly — a set has no guaranteed order, so printing one reliably means converting it to a sorted list first — and ends with a combined exercise where the actual skill being tested is choosing the right tool for each of several different questions about the same data.