17. Python Chapter 6 — arrays, lists and dictionaries - revision mindmap
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Choose a collection
- School array: indexed, typically fixed and homogeneous
- Python list: dynamic mutable sequence
- Dictionary: key → value mapping
- Match structure to access and output requirements
List operations
- append versus extend
- insert, replace, remove and pop
- Membership searches values
- Mutation methods may return None; preserve required order
References and copies
- Assignment: same object
- Shallow copy: new outer container
- Nested objects may still be shared
- Fresh row per grid row prevents aliasing
Two-dimensional data
- Row/column convention and bounds
- Rows, columns and two diagonals
- Neighbours: candidate coordinates then bounds
- Simultaneous updates use old grid and a separate new grid
Dictionaries
- Unique hashable keys
- Insert/update/delete and lookup
- Missing key: KeyError versus get fallback
- Frequency count, maximum count and distinct tied outputs
Worked example & exam traps
- a = [1,2]; b = a; b.append(3) → both names see [1,2,3].
- c = a[:] makes a new outer list; nested objects can remain shared.
- Fresh grid rows: [[0]*3 for _ in range(2)] creates two separate rows.
- Avoid: list = list.append(…); repeated row reference; dictionary membership tests values
Sources and reading
This map condenses Chapter 17 and its source trail. Use the self-learning reading guide for the corresponding VJC pages and A notes. It does not add topics to the stated promo scope.