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171 exercises

Shaping data

Records in, structure out. Grouping, merging, and the aliasing bugs that make a copy quietly not a copy.

12 exercisesdifficulty 2–4~240 min in total

—Exercises 12 exercises

Tally records by a field dict.get with a default, accumulating ~15 min Index records by a unique field dict as an index, detecting duplicates ~15 min Pull one field out of every record comprehension over records, a default that means absent ~12 min New names, same places rebuilding a dict, keeping order ~16 min The best few, without disturbing the rest sort stability, reverse= versus reversing ~18 min Reach into nested data safely walking nested dicts, defaults over exceptions ~20 min Group records by a field dict.setdefault, grouping ~20 min Turning a lookup around the inverse of a function, silent collisions ~20 min Sorting by several fields at once stable sort, successive passes ~24 min What changed between these two set algebra on keys, three-part results ~25 min Nested data, one level deep recursion over a tree, path building ~25 min Merge configuration, deeply recursion, deep vs shallow copy ~30 min