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3.6Choosing the Right Data Structure
| Need | Use | Why |
|---|---|---|
| Ordered collection of items | List / Array | Preserves order, allows duplicates |
| Key-value lookup | Dict / Object | O(1) lookup by key |
| Unique collection, membership checks | Set | O(1) membership check, automatic dedup |
| Immutable ordered data | Tuple | Cannot be accidentally modified |
| Counting occurrences | collections.Counter |
Histogram of values |
| Ordered dict (insertion order) | dict (Python 3.7+) |
Guaranteed insertion order |