Choosing a data structure

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Quick Questions

Shade in the A or B circle for each question.

1. You need to store the scores of 30 students in the order they were entered. Which structure fits best?

A A list: scores = [72, 85, 90]

B A tuple of student names stored as keys

2. You want to look up a student's phone number using their name. Which structure fits best?

A A dictionary: phones = {"Mia": "0412"}

B A list: phones = ["Mia", "0412"]

3. Which is the best choice to store the fixed latitude and longitude of Melbourne, which should never change?

A A list: location = [-37.81, 144.96]

B A tuple: location = (-37.81, 144.96)

4. True or false: A tuple is a good choice for a shopping list that you keep adding items to.

A False: use a list, because tuples cannot be changed

B True: tuples are the best for growing collections

5. You are storing 3 students, each with a name, a year level and a house. Which structure is best for the whole collection?

A A single tuple holding every name, year and house mixed together

B A list of dictionaries, one dictionary per student

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1scores = [85, 92, 78]		AA list: an ordered collection of values that you can loop through and change
2ages = {"Mia": 15, "Leo": 14}		BA dictionary: look up a value quickly using its key
3A tuple is best for a fixed group of values that should not change, like a map point		CA list is indexed by position, not by name. To look up by a key, use a dictionary instead.
4A list of dictionaries is best for storing records, where each dictionary holds one item's details		Dstudents = [{"name": "Mia", "year": 9}]
5colours = ("red", "blue") colours.append("green")		Epoint = (10, 25)
6phone = ["Mia", "0412 345 678"] print(phone["Mia"])		FA tuple cannot be changed, so append() causes an error. Use a list if the values need to grow.

Definitions

list, dict, tuple

Fill in the Blanks

Complete each line of code by filling in the missing parts.

ages = {"Mia": 15, "Leo": 16} print(____["Mia"])

rgb = _____([255, 128, 0])

kids = [{"age": 9}, {"age": 12}] print(kids[_]["age"])

stock = {"apple": 4, "pear": 7} print(stock.___("pear"))

names = ["Zoe", "Sam", "Ali"] for name in _____: print(name)

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A scores = (85, 92, 78)

B scores.append(90)

C print(scores[0])

Question 2

A ages = {"Mia": 15, "Leo": 16}

B print(ages[0])

C print(len(ages))

Question 3

A RGB = (255, 128, 0)

B RGB[0] = 200

C print(red)

Question 4

A student = ["name": "Ava"]

B student["year"] = 10

C print(student["name"])

Question 5

A dog = {"name": "Rex"}

B cat = {"name", "Kit"}

C pets = [dog, cat]

D print(pets[1]["name"])

Answer Key

Choosing a data structure

Section A: Quick Questions

A — A list: scores = [72, 85, 90]

A — A dictionary: phones = {"Mia": "0412"}

B — A tuple: location = (-37.81, 144.96)

A — False: use a list, because tuples cannot be changed

B — A list of dictionaries, one dictionary per student

Section B: Match the Pairs

scores = [85, 92, 78] → A list: an ordered collection of values that you can loop through and change

ages = {"Mia": 15, "Leo": 14} → A dictionary: look up a value quickly using its key

A tuple is best for a fixed group of values that should not change, like a map point → point = (10, 25)

A list of dictionaries is best for storing records, where each dictionary holds one item's details → students = [{"name": "Mia", "year": 9}]

colours = ("red", "blue") colours.append("green") → A tuple cannot be changed, so append() causes an error. Use a list if the values need to grow.

phone = ["Mia", "0412 345 678"] print(phone["Mia"]) → A list is indexed by position, not by name. To look up by a key, use a dictionary instead.

Section C: Definitions

list, dict, tuple — Pick the structure by how you use the data: a list for an ordered collection, a dict for lookup by key, and a tuple for a fixed group of values that should not change.

Section D: Fill in the Blanks

ages = {"Mia": 15, "Leo": 16}
print(ages["Mia"])

rgb = tuple([255, 128, 0])

kids = [{"age": 9}, {"age": 12}]
print(kids[0]["age"])

stock = {"apple": 4, "pear": 7}
print(stock.get("pear"))

names = ["Zoe", "Sam", "Ali"]
for name in names:
    print(name)

Section E: Spot the Error

A — Scores is an ordered collection that grows, so it needs a list. A tuple is fixed and has no append(), so line 2 would fail. It should be scores = [85, 92, 78].

B — A dictionary is looked up by key, not by position number. There is no key 0, so this causes a KeyError. It should be print(ages["Mia"]).

B — A tuple holds a fixed group of values and cannot be changed after it is created. Assigning to RGB[0] causes a TypeError. The line should read the value: red = RGB[0].

A — Key: value pairs belong in a dictionary, which uses curly brackets. Square brackets make a list, which cannot hold key: value pairs. It should be student = {"name": "Ava"}.

B — A dictionary needs a colon between the key and the value. A comma makes a set of two strings instead of a record. It should be cat = {"name": "Kit"}.