Year 11 Computing — Dictionaries and their keys

1.A key the dictionary did not have is written to here. What does this program print?

stock = {"pen": 12, "book": 5}
stock["bag"] = 9
print(len(stock))

2.A dictionary called scores holds {"red": 14, "blue": 6, "green": 22, "black": 9}. Put these lookups in order of the number each one gives, smallest first.

• scores["blue"]
• scores["red"]
• scores["green"]
• scores["black"]

3.This dictionary starts with nothing in it at all. What does this program print?

seen = {}
seen["pen"] = 2
seen["bag"] = 5
print(len(seen))

4.You want to find one particular thing that a program has stored. What is the difference between a list and a dictionary here?

• a) A dictionary is looked in by position as well, starting from 0 like a list does
• b) A list can hold only numbers, and a dictionary only writing
• c) A list is looked in by position, and a dictionary by a key that whoever wrote the program chose
• d) A dictionary numbers its keys as they go in, so its first key is key 0

5.This line looks just like the last one, but the key it writes to is not new. What does this program print?

counts = {"red": 3, "blue": 8}
counts["red"] = 10
print(len(counts))

6.Two values are looked up and added together. What does this program print?

weights = {"box": 25, "bag": 40, "cup": 5}
print(weights["box"] + weights["cup"])

7.A value is looked up by name rather than by position here. What does this program print?

prices = {"pen": 10, "book": 45, "bag": 90}
print(prices["book"])

8.One of these two lines adds a pair and the other one does not. What does this program print?

stock = {"pen": 6}
stock["book"] = 3
stock["pen"] = 11
print(stock["pen"] + stock["book"])