Python Lists and Tuples Quiz: Sorting, Grids and deque Test

Instructions

This checkpoint covers the whole module: lists and their method costs, aliasing and shallow versus deep copies, comprehensions in list, set, dict and generator form, sorting with keys and stability and bisect, tuples and unpacking with namedtuple, grids with neighbours, transposes and the multiplication trap, and the sequence tools with deque and the sequence protocol.

How it works. Twelve questions and three programs. You need 70% on the questions and every program accepted to clear the module. You can retake it as often as you like; your best score counts.

Before you start, make sure you can answer these from memory:

• Which list operations are O(1) and which are O(n), and what replaces pop(0)?
• After b = a.copy() for a list of lists, what is shared?
• What is the difference between [x for x in xs if c] and [x if c else y for x in xs]?
• Why does rows.sort(key=name); rows.sort(key=score, reverse=True) give score-then-name order?
• What does first, *rest = [1] bind?
• Why is [[0] * C] * R wrong, and what is right?
• Which two methods make a class usable with len, indexing, iteration and in?

The three programs are an inventory that is edited, sorted by several keys and reported in aligned columns, a grid simulation that counts live neighbours with a direction list and a bounds check, and a sliding-window statistics tool built on a bounded deque.

Common questions

After b = a.copy() for a list of lists, what is shared?

The inner lists. copy() is shallow: b is a new outer list holding references to the same row objects, so b[0].append(9) also changes a[0]. Rebinding b[0] = [0] leaves a alone, and copy.deepcopy(a) shares nothing.

Why does sorting by name and then by score descending give score-then-name order?

Python's sort is stable, so the second sort, by score, keeps rows with equal scores in the order the first sort left them — alphabetical by name. Sorting by the secondary key first and the primary key last composes a multi-key order, even with reverse=True.

What does first, *rest = [1] bind?

first is 1 and rest is an empty list. A starred target collects whatever is left over as a list, and that list may be empty; Python raises ValueError only when a plain target has no value left to take.

Exercises

add bolt 100 0.05
add nut 250 0.02
restock bolt 50
remove screw
report

unknown item
nut         250    0.02      5.00
bolt        150    0.05      7.50
TOTAL                       12.50

3 4
##..
#..#
..##

islands 2
largest 3

ada 50
bob 70
cy 60
ada 80

ada
bob,ada
bob,cy,ada
ada,bob,cy

In this module: Lists, tuples and sequences

• Lists — the mutable sequence
• Comprehensions — building collections from expressions
• Sorting — sort, sorted, keys, stability and bisect
• Tuples, unpacking and named tuples
• Grids and nested lists
• The sequence tools — enumerate, zip, reversed, any, all, deque and the protocol
• Checkpoint — Lists, tuples and sequences (this lesson)