Free practice · matching · easy
Practice
Match collection tools to purposes
Match each collection tool to the data relationship it represents.
Collection contract
Choose access by the relationship the data represents
- List
- Ordered items accessed by index or iteration
- Dictionary
- Values accessed by stable keys
- Boundary
- Empty, one-item, and several-item states
- Mutation
- One deliberate, traceable change
- Reconciliation
- Expected size, keys, counts, and totals
Lists use ordered positions; dictionaries use meaningful keys. Both need shape, missing-data, mutation, and boundary checks.