Hyperparameter Combinations (Cartesian Product)

Given a dict of hyperparameter name → list of candidate values, generate every combination (one value per key). ML Platform asks this directly; the follow-up is to enumerate test cases the function should be exercised on. Requirements Given input of the form parameters = { "learning_rate": [0.1, 0.2, 0.3], "feature": ["A", "B", "C"], "batch": [10, 20, 30], "depth": [100, 200, 300], } produce every combination, one value per key: {"learning_rate": 0.1, "feature": "A", "batch": 10, "depth": 100} {"learning_rate": 0.1, "feature": "A", "batch": 10, "depth": 200} ... {"learning_rate": 0.3, "feature": "C", "batch": 30, "depth": 300} The ML Platform variant adds a test-case design follow-up: list the inputs you would exercise the function on (empty dict, single key, empty list under a key, large key count). Examples With the input above the output has 3 × 3 × 3 × 3 = 81 combinations. Notes Two equally accepted implementations: recursive enumeration (pick a key, recurse on the remaining keys, prepending each value of the current key to each suffix combination) or itertools.product over the values, zipped with keys at emission time. The interviewer typically pushes for an iterator / generator version so the consumer can stream combinations without materializing the full list — important when the cardinality explodes (a 6-key grid with 5 values each is already 15,625 combinations). Test cases the interviewer wants to hear: empty dict (one empty combination, or zero, define which), key mapped to empty list (zero combinations), single-key dict, one key with one value, very large cardinality (does the iterator stay constant-memory?). Preparation Write both implementations once. The recursive version is the harder one to keep clean; the generator version is the more idiomatic-Python answer. Verbally enumerate 5 test cases in 60 seconds and explain what each one stresses. The follow-up is graded. For a Java-flavored alternate, practice the recursive version with a List<Map<String, Object>> accumulator and a single key-ordering pass.