Summary

Conclusions

A list is convenient for a mutable sequence, a tuple for a fixed record, a set for uniqueness, and a dictionary for access by key. Counter, defaultdict, and deque simplify common operations when their behavior matches the problem's rules. Copying, order, and hashability are part of the program's contract.

Self-check questions

1. Which properties distinguish lists, tuples, sets, and dictionaries?
2. How does an out-of-bounds index differ from an out-of-bounds slice?
3. How does a negative step work, and why is step=0 prohibited?
4. How does append differ from extend?
5. What do sort, sorted, and pop return?
6. Why is sorting by a tuple of keys convenient for a ranking?
7. How do you build independent matrix rows?
8. What does copy copy, and what does deepcopy copy?
9. Why is a tuple containing a list unsuitable as a dictionary key?
10. How do set difference and symmetric difference differ?
11. When do get and setdefault have different effects on a dictionary?
12. Which collection changes are dangerous during iteration?
13. How does Counter.subtract differ from the subtraction operator?
14. What are maxlen, OrderedDict, and ChainMap used for?
15. Why is insort O(n) even though finding the position is O(log n)?

Useful links

• https://docs.python.org/3.14/tutorial/datastructures.html
• https://docs.python.org/3.14/library/stdtypes.html
• https://docs.python.org/3.14/library/collections.html
• https://docs.python.org/3.14/library/copy.html
• https://docs.python.org/3.14/library/heapq.html
• https://docs.python.org/3.14/library/bisect.html